Category Archives: Environmental engineering

What Biochemical Oxygen Demand (BOD) Measures?

What Biochemical Oxygen Demand measures are a question that all of us have in our minds while learning about water pollution. In this blog, I will walk you through Biochemical Oxygen Demand and, and its significance. The concept of Dissolved Oxygen is described in detail in the upcoming paragraphs.  In the next section, I will show you the complete details about what actually the Biochemical Oxygen Demand measures.

  1. What does the Biochemical Oxygen Demand measure?
    1. Total Biochemical Oxygen Demand Measures
    2. Biochemical Oxygen Demand Measures of Drinking Water
    3. Factors affecting Biochemical Oxygen Demand
  2. Dissolved Oxygen (DO)
    1. Dissolved Oxygen Determination
    2. Calculation of Biochemical Oxygen Demand
    3. BOD5 vs BOD20

What does the Biochemical Oxygen Demand measure?

Biochemical Oxygen Demand measures the amount of oxygen that the microbes utilize to degrade organic materials in a water body. Also, Biochemical Oxygen Demand measures the chemical oxidation of inorganic materials i.e., the removal of oxygen from water via a chemical reaction. 

The BOD value is generally expressed in milligrams of oxygen used per litre of the sample over a 5-day incubation period at 20 °C, and it is frequently used as an estimate of the degree of organic pollution in water. The reduction of BOD is used in evaluating the efficacy of wastewater treatment systems.

The main sources of BOD in wastewater include leaves and woody debris, plant and animal carcass, animal manure, effluents from pulp and paper mills, wastewater treatment plants, food-processing plants, failing septic systems, and urban stormwater runoff.

Biochemical Oxygen Demand in wastewater
Biochemical Oxygen Demand in wastewater

Biochemical Oxygen Demand has a direct effect on the amount of dissolved oxygen in rivers and streams. The higher the BOD, the faster the rate of oxygen depletion in the stream. This results in higher forms of aquatic life having less oxygen available to them. As a result, they suffocate, and eventually, die.

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Total Biochemical Oxygen Demand Measures

Total biochemical oxygen demand is the quantity of oxygen necessary to totally oxidise organic substances to carbon dioxide and water over generations of microbial development, death, degradation, and cannibalism. It has a greater impact on food webs than water quality.

Biochemical Oxygen Demand Measures of Drinking Water

A water sample having a BOD5 between 1 and 2 mg/l indicates very pure water, 3.0 to 5.0 mg/l means moderately clean water and > 5 mg/l indicates a neighbouring pollution source. The biochemical oxygen demand of safe drinking water must be 1-2 mg/l.

Factors affecting Biochemical Oxygen Demand

Temperature, nutrient concentrations, aeration and the enzymes available to indigenous microbial populations affect the BOD measurements. For instance, rapids and waterfalls will speed up the decomposition of organic and inorganic material in stream water. As a result, BOD levels at a sampling location with slower, deeper waters may be higher for a given volume of organic and inorganic material than at a similar site in highly aerated waters.

Chlorine can interfere with the BOD measurements by preventing or killing the microorganisms that break down the organic and inorganic substances in a sample. Therefore, use sodium thiosulfate to neutralise the chlorine while sampling in chlorinated waters, such as those below a sewage treatment plant’s effluent.

Algae in the wastewater affect the Biochemical Oxygen Demand measures by releasing extra oxygen into the wastewater during photosynthesis. Hence, perform the BOD test in complete darkness. Before delving into Biochemical Oxygen Demand measures we should first understand the concept of Dissolved Oxygen (DO), its significance and its measurement.

Dissolved Oxygen (DO)

Aquatic plants and algae release oxygen into the water after performing photosynthesis in the presence of sunlight. The aquatic animals breathe this dissolved oxygen. Also, some oxygen from the atmosphere continuously dissolves into the water through reaeration. These three processes are in equilibrium and maintain the level of oxygen in water bodies at the required levels.

When organic substances or pollutants enter the waterbody, it disturbs the dissolved oxygen balance since microbes utilize dissolved oxygen in its breakdown. In other words, these organic substances exert a demand on the available dissolved oxygen.

Dissolved Oxygen - Aquatic plants & Algae
Dissolved Oxygen – Aquatic plants

The greater the oxygen necessary for its breakdown, the greater would be the reduction in the dissolved oxygen in the water body. Pollution occurs when the oxygen demand exceeds the dissolved oxygen availability.

Also read: Wastewater Treatment- Stages and Process full details

Dissolved Oxygen Determination

Winkler’s method helps in determining the dissolved oxygen. The principle behind this method is the reaction between dissolved oxygen and manganese ions to precipitate out manganese dioxide.

Mn2+ + O2 —-> MnO2 

The manganese dioxide then reacts with iodide ions. This reaction liberates iodine in an amount chemically equivalent to the original dissolved oxygen.

MnO2 + 2I + 4H+ —-> Mn2+ + I2 + 2H2O

Titration with sodium thiosulphate gives the amount of iodine liberated and thereby the equivalent dissolved oxygen content. Thus we can measure the amount of Dissolved Oxygen in a given water sample.

Now, you have got a clear idea about Dissolved Oxygen. In the next section, I will show you the complete details about what actually the Biochemical Oxygen Demand measures.

Next, let’s see the procedure to obtain the Biochemical Oxygen Demand measures.

Calculation of Biochemical Oxygen Demand

We require two samples from a location to measure Biochemical Oxygen Demand. One is immediately tested for dissolved oxygen, while the other is incubated in the dark at 20o Celsius for 5 days before being examined for the residual dissolved oxygen. 

Let me show you the detailed procedure.

  1. Fill two standard 300-ml BOD bottles with the sample wastewater. Seal the bottles properly.
  2. Immediately determine the dissolved oxygen content of one of the samples using Winkler’s method.
  3. Incubate the second bottle at 20 0C for 5 days in complete darkness.
  4. Determine the DO levels after 5 days.

The amount of BOD is the difference in oxygen levels between the first and second tests, measured in milligrams per litre (mg/L). This is the amount of oxygen that the microorganisms require throughout the incubation period to break down the organic materials in the sample container.

DO (mg/L) of first bottle – DO (mg/L) of second bottle = BOD (mg/L)

The dissolved oxygen level may be nil at the end of the 5-day incubation period. This is particularly the case for rivers and streams which have a high pollution load of organic matter. Moreover, it is impossible to determine the BOD level because it is unknown when the zero point was reached. In this situation, dilute the original sample by a factor that yields a final dissolved oxygen content of at least 2 mg/L. The dilutions should be done with special dilution water of high purity.

The dilution water consists of deionised water with sufficient nutrients, phosphate buffer, trace elements and seed organisms (mostly settled domestic sewage). Perform a blank run on this dilution water and subtract its oxygen demand from the results.

BOD5 (mg/l) = D* [(DOt=0 – DOt=5)]sample – [(DOt=0 – DOt=5)]blank

BOD5 vs BOD20

During the standard 5-day/20 0Celsius conditions, about two-thirds of the carbonaceous material undergoes degradation. In the 5-day test, compounds that aren’t easily biodegradable or soluble don’t undergo complete digestion. Incubation of 5 days gives the soluble BOD or BOD5 measures while that of 20 days gives Ultimate Biochemical Oxygen Demand measures or BOD20

Biochemical Oxygen Demand
Biochemical Oxygen Demand

It requires nearly 20 days for the complete breakdown. On the other hand, the 20-day Biochemical Oxygen Demand measures greater long-term oxygen demand from insoluble materials including cellulose, long-chain fatty acids, and grease. Always keep in mind that COD > BOD20 > BOD5.

In spite of its limitations, Biochemical Oxygen Demand analysis has wide applications in monitoring pollution. These days, Chemical Oxygen Demand analysis is gaining wide popularity for research and plant control.

That’s it about Biochemical Oxygen Demand. Hope you found it insightful. Let us know your queries in the comments.

The Ozone Layer Depletion – Effects and Causes

Ozone Layer Depletion was a problem that started haunting environmentalists and the common people alike since the 1980s. In this blog, let me show you what is the ozone layer, its role, causes and effects of its depletion.

What is the Ozone Layer?

The ozone layer is an area of the earth’s stratosphere that contains high levels of ozone (O3) and protects the planet from the sun’s harmful ultraviolet rays. It can absorb roughly 97-99 percent of the sun’s damaging UV radiation, which otherwise can kill life on the Earth.

Ozone layer

Ozone

Ozone is an allotrope of oxygen and is much less stable than the common diatomic allotrope O2. Hence it easily breaks down to O2 breaking down in the lower atmosphere. Ozone is formed from dioxygen under the action of ultraviolet (UV) light and electrical discharges in the Earth’s atmosphere. The process of ozone creation and destruction is called the Chapman cycle.

2 O3 → 3 O2

We can find ozone in both the upper (stratosphere) and lower layers (troposphere) of the atmosphere. The troposphere is the layer closest to the Earth’s surface. The troposphere typically reaches a height of about 6 miles, where it meets the stratosphere, the second layer. Depending on its location in the atmosphere, ozone can be “good” or “bad” for your health and the environment.

Tropospheric Ozone

Ground-level ozone, sometimes known as “bad” ozone, is a toxic atmospheric pollutant that affects crops, trees, and other vegetation. It is a major contributor to urban smog.

It forms when sunlight reacts with air containing hydrocarbons and nitrogen oxides either directly at the source of pollution or many kilometers downwind. Photolysis of ozone by UV light produces the hydroxyl radical HO•, which is the initial step in the formation of smog components such peroxy acyl nitrates.

Ozone works as a greenhouse gas by absorbing some of the earth’s infrared radiation. Tropospheric ozone has an annual global warming potential of 918 to 1022 tones of carbon dioxide equivalent/tons tropospheric ozone. This suggests that ozone in the troposphere has a radiative forcing effect 1,000 times stronger than carbon dioxide on a per molecule basis.

However, tropospheric ozone is a short-lived greenhouse gas that degrades faster in the atmosphere than carbon dioxide. Hence, in the long run, it doesn’t cause as much harm as Carbon Dioxide.

Stratospheric Ozone

We can find the highest levels of ozone in the stratosphere, in a region also known as the ozone layer. This region extends between about 10 km and 50 km above the surface of Earth. This is “good ozone” which absorbs almost the entire UV-B band (280–315 nm). If the UV-B reaches the Earth’s surface it can cause damage to humans and other organisms including sunburns and skin cancers.

Scientists, on the other hand, have identified a hole in the ozone layer over Antarctica. Let me explain how ozone layer depletion occurs.

Also read: Acid Rain – Definition, Causes, Effects, and Solutions

Ozone Layer Depletion

Ozone Layer Depletion is the gradual thinning of the earth’s ozone layer in the upper atmosphere caused by chemical compounds containing gaseous bromine or chlorine from industry or other human activities.

When chlorine and bromine atoms in the atmosphere come into contact with ozone, the atoms destroy the ozone molecules. One molecule of chlorine can destroy 100,000 ozone molecules. It depletes faster than it forms.

Ozone layer depletion

Also read: What are air pollutants? | Types, sources and effects of air pollution

Certain chemicals on exposure to intense ultraviolet radiation, emit chlorine and bromine, which contributes to the ozone layer’s depletion. Ozone Depleting Substances are substances that deplete the ozone layer (ODS). Following are some chemicals that fall under the category of ODS.

  • Chlorofluorocarbons (CFCs)
  • Hydrochlorofluorocarbons (HCFCs)
  • Bromofluorocarbons
  • Hydrobromofluorocarbon (HBFCs)
  • Halons
  • Methyl bromide
  • Carbon tetrachloride

The Ozone Layer Hole

Due to a lack of sunshine and a restricted mixing of lower stratospheric air above Antarctica with the air outside the region, the air over the Antarctic gets exceptionally chilly during the winter. The circumpolar vortex, often known as the polar winter vortex, is a large area of low pressure and cold air surrounding both of the Earth’s poles. It is responsible for this poor mixing.

Polar Stratospheric Clouds (PSC) originate at altitudes of 12 to 22 kilometers as a result of the exceptionally cold temperatures inside the vortex above the poles. PSC particles undergo chemical processes that change the less reactive chlorine-containing molecules into more reactive forms like molecular chlorine (Cl2), which accumulate throughout the polar winter. These cloud particles can also react with bromine-containing chemicals and nitrogen oxides.

When the sun returns to Antarctica in the early spring, the molecular chlorine breaks down into single chlorine atoms, which can combine with and destroy ozone. The breakdown of ozone continues until the polar vortex breaks up, which generally happens in November. Hence there is a vast area over the Antarctic region where the ozone layer underwent considerable depletion and is extremely thin. We commonly refer to this as the ‘ozone hole‘.

Chemistry of the Ozone Layer Depletion

Because of their poor reactivity, chlorofluorocarbons can rise to the stratosphere without undergoing degradation in the troposphere. UV light liberates the Cl and Br atoms from the parent molecules once they reach the stratosphere, e.g.

CFCl3 + electromagnetic radiation → Cl· + ·CFCl2

Ozone is a highly reactive molecule that can rapidly reduce to a more stable oxygen form with the help of a catalyst. Cl and Br atoms destroy ozone molecules in several catalytic reactions. An ozone molecule (O) reacts with a chlorine atom forming chlorine monoxide (ClO) from an oxygen atom and leaving an oxygen molecule (O2).

Cl· + O3 → ClO + O2

The ClO can react with a second molecule of ozone to release the chlorine atom and produce two oxygen molecules.

ClO + O3 → Cl· + 2 O2

The chlorine is free to repeat this two-step cycle. The overall effect is a decrease in the amount of ozone.

Ozone Layer Depletion Causes

Depletion of the ozone layer is a great concern that is linked to a variety of causes. The following are the primary factors that contribute to the ozone layer’s depletion:

Chlorofluorocarbons

The main source of ozone layer depletion is chlorofluorocarbons or CFCs. Solvents, spray aerosols, freezers, and air conditioners, among other things, emit these chlorofluorocarbons. The ultraviolet radiations in the stratosphere break down chlorofluorocarbon molecules, releasing chlorine atoms. These atoms degrade ozone by reacting with it as we had seen above.

Unregulated Rocket Launches

According to studies, the unregulated launch of rockets depletes the ozone layer far more than CFCs do. If not addressed, this might result in a significant depletion of the ozone layer by 2050. Increased international space launches, as well as the possibility of a commercial space travel boom, may soon make rockets the worst offenders in terms of ozone depletion.

When solid-fuel rockets blast off, it releases chlorine gas directly into the stratosphere, where it interacts with oxygen to produce ozone-depleting chlorine oxides.  Rocket oxidizer contains soot and aluminium oxide, which depletes upper-atmosphere ozone, which protects the Earth’s surface from harmful ultraviolet rays.

Natural Factors

Certain natural phenomena, such as Sunspots and stratospheric winds degrade the ozone layer. However, it only contributes to roughly 1-2 percent of ozone layer depletion. Volcanic eruptions are also to blame for the ozone layer’s depletion.

Ozone Layer Depletion Effects

The following are the devastating effects of ozone depletion.

Higher Levels of UV

While ozone is a minor component of the Earth’s atmosphere, it is responsible for the majority of UV-B absorption. With increasing slant-path thickness and density, the amount of UVB radiation that penetrates the ozone layer falls rapidly. [58] Higher levels of UVB reach the Earth’s surface as stratospheric ozone levels fall.

Increased ozone in the troposphere

Increased surface UV causes increased tropospheric ozone. Since ozone is hazardous due to its powerful oxidant capabilities, ground-level ozone is well recognised as a health hazard. Young children, the elderly, and individuals with asthma or other respiratory problems are especially vulnerable. At this time, the action of UV radiation on combustion gases from car exhausts is the primary source of ozone at ground level.

Crop-related effects

An increase in UV radiation is likely to have an impact on crops. For the retention of nitrogen, many commercially significant plant species, such as rice, rely on cyanobacteria living on their roots. Cyanobacteria are sensitive to UV light and this, in turn, can affect the nitrogen retention of rice plants.

Biological consequences



The impacts of increasing surface UV radiation on human health have been the principal public worry about the ozone hole. Exposure to UV radiation can cause Basal and squamous cell carcinomas, Malignant melanoma and Cortical cataracts.

Effect on plants

The stress that plants suffer when exposed to UV radiation is another key effect of ozone depletion on plant life. This can lead to a decline in plant development and an increase in oxidative stress. Reduced plant growth will have long-term repercussions, including a drop in the amount of carbon that plants capture and sequester from the environment.

Furthermore, when plants are exposed to excessive quantities of UV light, they emit isoprenes into the air, which contributes to air pollution and increases the quantity of carbon in the atmosphere, ultimately contributing to climate change.

As scientists and world leaders became aware of ozone depletion and its damaging effects, they signed an international agreement to revive the ozone layer. Let’s have a closer look into it.

Also read: Environmental Laws of India – A Complete Guide

The Montreal Protocol

  • The Montreal Protocol or Montreal Protocol on Substances that Deplete the Ozone Layer was adopted in 1987 as part of the Vienna Convention. It promotes international cooperation in reversing the rapid drop in ozone concentrations in the atmosphere.
  • To honour the signing of the Montreal Protocol on 16th September 1987, the United Nations General Assembly designated September 16 as International Day for the Preservation of the Ozone Layer, or “World Ozone Day,” in 1994.
Reversing ozone layer depletion

Conclusion

The ozone layer is a protective umbrella around our mother Earth and saves us from the damaging radiations of the Sun. Let’s join our hands to keep the ozone layer intact for our future generations as well.

That’s it about ozone layer depletion. Happy Learning!

Environmental Laws of India – A Complete Guide

The environmental Laws of India help to ensure the protection of the environment and other natural resources and to prevent pollution. In this blog, we will discuss the major Environmental Laws of India and their provisions. Let’s begin with the background of the formation of Environmental Laws and the Ministry of Environment and Forests (MoEF).

Ministry of Environment and Forests (MoEF)

India’s constitutional framework and international commitments clearly reflect the necessity for environmental protection and conservation, as well as the sustainable use of natural resources. As we all know, Part IVA (Article 51A-Fundamental Duties) of the Indian Constitution imposes a duty on every Indian citizen to safeguard and improve the natural environment, including forests, lakes, rivers, and animals, as well as to have compassion towards living beings.

Environment and forest

Following the Stockholm Conference, the Department of Science and Technology established the National Council for Environmental Policy and Planning in 1972 as a regulatory agency to oversee environmental issues. Later, the Council became a full-fledged Ministry of Environment and Forests (MoEF).

The Ministry of Environment and Forestry (MoEF) was created in 1985. It is now the country’s primary administrative authority for regulating and ensuring environmental protection. MoEF also establishes the legal and regulatory framework for it.

A variety of environmental laws have been in effect since the 1970s. The following comprise the country’s regulatory and administrative core for environmental protection:

  • The Ministry of Environment and Forests (MoEF)
  • The CPCB, Central Pollution Control Board
  • SPCBs, State Pollution Control Boards

The National Green Tribunal Act, 2010

The National Green Tribunal Act, 2010 (NGT Act) was enacted with the goal of establishing a National Green Tribunal (NGT). The NGT shall ensure the effective and timely resolution of issues connected to environmental protection and other natural resource conservation. Along with that, it deals with civil cases that come under the following Environmental Laws of India:

National Green Tribunal
  • The Water (Prevention and Control of Pollution) Act, 1974,
  • The Water (Prevention and Control of Pollution) Cess Act, 1977,
  • The Forest (Conservation) Act, 1980,
  • The Air (Prevention and Control of Pollution) Act, 1981,
  • The Environment (Protection) Act, 1986,
  • The Public Liability Insurance Act, 1991 and
  • The Biological Diversity Act, 2002.

The NGT does not have jurisdiction over two major acts:

  • The Wildlife (Protection) Act of 1972
  • The Scheduled Tribes and Other Traditional Forest Dwellers (Recognition of Forest Rights) Act of 2006.

This limits the NGT’s authority and, makes it difficult for it to function. The Act came into effect on October 18, 2010.

The Water (Prevention and Control of Pollution) Act, 1974

  • The Water (Prevention and Control of Pollution) Act of 1974 (the “Water Act”) was enacted to prevent and control water pollution and to maintain or restore the wholesomeness of water in the country.
  • Also, it established Boards for the prevention and control of water pollution in order to carry out the aforementioned objectives.
  • The Water Act makes it illegal to dump pollutants into water bodies beyond a certain level. And, it imposes penalties for non-compliance.
  • The CPCB was established at the national level by the Water Act. It establishes requirements for the prevention and management of water pollution.
  • SPCBs work under the direction of the CPCB and the State Government at the state level.

Also read: What are Water Pollutants? – Definition, Sources, and Types

  • In 1977, the Water (Prevention and Control of Pollution) Cess Act was enacted to provide for the imposition and collection of a cess on water consumed by persons engaged in certain types of industrial operations.
  • The Government collects this tax to supplement the funds available to the Central Board and State Boards for the prevention and control of water pollution.

The Air (Prevention and Control of Pollution) Act, 1981

  • The Air (Prevention and Control of Pollution) Act, 1981 (the “Air Act”) establishes boards at the national and state levels to prevent, control, and abate air pollution.
  • This act established ambient air quality standards to combat the difficulties connected with air pollution.
  • It aims to reduce air pollution by forbidding the use of polluting fuels and substances, as well as regulating air-polluting appliances.
  • The Air Act allows the State Government to proclaim any place or area within the State as an air pollution control area or areas after consulting with the SPCBs.
  • SPCBs must consent to the establishment or operation of any industrial facility in the pollution control area under the Act.
  • SPCBs will also check pollution control equipment and production processes. It can also test the air in air pollution control areas.

If you wish to know more about air pollution, do check out our blogs on air pollution: Air Pollution Effects and Causes – A complete overviewAir Pollution Causes – A Comprehensive Guide

The Environment Protection Act, 1986

  • The Environment Protection Act of 1986 (the “Environmental Act”) establishes a framework for investigating, planning, and executing long-term environmental safety regulations.
  • It creates a framework for the coordination of federal and state bodies established under the Water Act and the Air Act.
  • Under the Environment Act, the Central Government can take measures to protect and improve the environment’s quality by establishing standards for emissions and discharges of pollution into the atmosphere.
  • It can also regulate the location of industries; manage hazardous wastes; and protect public health and welfare.
  • The Central Government provides notices under the Environment Act for the protection of ecologically vulnerable areas from time to time, as well as guidance for issues covered by the Act.

Also read: Environmental Impact Assessment (EIA) – Process and Benefits

Conclusion

Mere implementation of Environmental Laws doesn’t guarantee the conservation of forests and other natural resources. Strict implementation of these laws, stringent punishment of the defaulters, and creating awareness among the public about the provisions of the laws are also needed for protecting our environment. It is our duty to preserve the natural resources and transfer them to our future generations with the same wholesomeness and greenery.

That was it about the Environmental Laws of India. In case of any queries, please feel free to ask in the comments. Happy Learning.

Biomass Energy – Definition, Advantages and Future

Biomass Energy is hailed as a renewable source of energy and a method for sustainable waste disposal. In this blog, I will show you the definition of biomass energy, its feedstock, its advantages, disadvantages, and the various methods available for its thermal conversion.

Let’s begin by understanding the definition of biomass energy.

Biomass Energy Definition

Biomass energy is energy generated or produced by living or once-living organisms. Plants receive the sun’s energy through photosynthesis and transform carbon dioxide and water into nutrients. They store this energy in biomass (carbohydrates).

We can convert this stored energy into useable energy in both direct and indirect ways. We can burn biomass directly to provide heat, turn it directly to electricity, or process it into biofuel (indirect).

Biomass Energy Source Examples

Today, wood and wood wastes are the most common biomass energy source. We can burn wood directly or convert it into pellet fuel or other fuel forms to generate energy. Other plants that can serve as fuel include corn, switchgrass, miscanthus, and bamboo. Wood waste, agricultural waste, municipal solid waste, manufacturing waste, sewage sludge, and landfill gas are the most common waste energy feedstocks.

Biomass energy
Biomass energy

Conversion of Biomass to Thermal Energy

Thermal conversion involves the application of heat to convert biomass to energy. The biomass feedstock is heated to burn, dehydrate, or stabilize by thermal conversion. Raw materials such as municipal solid waste (MSW) and scraps from paper or timber mills are the most common biomass feedstocks for thermal conversion.

The following processes produce different types of energy from biomass:

  • Direct firing
  • Co-firing
  • Pyrolysis
  • Gasification
  • Anaerobic decomposition

We must dry the biomass first before burning it. This process is called torrefaction. We heat biomass to around 200° to 320° Celsius (390° to 610° Fahrenheit) during torrefaction. The biomass dries out to the point that it can no longer absorb moisture and rot. It loses around 20% of its original bulk but keeps 90% of its original energy.

Torrefaction turns biomass into a dry, blackened substance from which we make briquettes. Briquettes made from biomass are hydrophobic, which means they reject water. This allows their storage in damp environments. The briquettes have a high energy density and are simple to burn when used in direct or co-firing applications.

Also read: Solar Energy- Definition, Advantages and Future

Direct Firing and Co-Firing

The majority of briquettes from torrefaction undergo direct burning. The steam generated during the firing process drives a turbine, which in turn drives a generator, which generates energy. This electricity can power machines or heat structures.

Biomass can also undergo co-firing, which means burning the briquettes along with fossil fuel. Biomass undergoes frequent co-firing with coal in power facilities. Co-firing reduces the requirement for additional biomass processing facilities and the demand for coal as well. Also, it reduces the amount of carbon dioxide and other greenhouse gases released by burning fossil fuels.

Pyrolysis

We heat biomass to 200° to 300° C (390° to 570° F) in the absence of oxygen during pyrolysis. This prevents it from combusting and changes the chemical composition of the biomass. Pyrolysis creates pyrolysis oil, a synthetic gas known as syngas, and a solid residue known as biochar.

Bio-oil

Pyrolysis oil or bio-oil is a form of tar. It finds application as a component in various fuels and plastics and gives energy upon burning. Scientists and engineers are researching pyrolysis oil as a possible substitute for petroleum.

Syngas

Syngas finds application as a fuel such as synthetic natural gas. It can also be converted to methane and used as a natural gas substitute. Clean syngas can be used for heat or energy or processed into biofuels, chemicals, and fertilizers for transportation.

Also read: Tidal Energy – Definition, Advantages, and Future

Biochar

The solid residue we obtain after the pyrolysis of biomass feedstock is biochar. Biochar has a number of merits over ordinary biomass feedstock. Let’s have a look at them.

  • When biomass burns or decomposes naturally or as a result of human action it releases large amounts of methane and carbon dioxide into the atmosphere. Biochar, on the other hand, sequesters or stores its carbon content. That is it is a great carbon sink. Carbon sinks are places that can store carbon-containing compounds, such as greenhouse gases.
  • When we reintroduce biochar to the soil, it can continue to absorb carbon and develop huge subsurface carbon sinks, resulting in negative carbon emissions and healthier soil.
  • Biochar carbon remains in the ground for centuries, slowing the growth in atmospheric greenhouse gas levels. Simultaneously, its presence in the earth can improve water quality, increase soil fertility, raise agricultural productivity, and reduce pressure on old-growth forests
  • Biochar also aids with soil enrichment. It is permeable and prevents pesticides and other nutrients from seeping into the runoff.

Gasification

Gasification directly converts biomass to energy. During gasification, we heat the biomass feedstock (typically Municipal Solid Waste) to over 700° C (1,300° F) with a controlled amount of oxygen. As the molecules break down, it produces the following two products:

  • Syngas
  • Slag

Anaerobic Decomposition

In landfills, anaerobic decomposition occurs when biomass is crushed and squeezed, resulting in an anaerobic (or oxygen-poor) environment. It is the breakdown of material by microbes, mainly bacteria, in the absence of oxygen.

Biomass decomposes in an anaerobic environment, producing methane, a useful energy source. This methane has the potential to replace fossil fuels.

Anaerobic decomposition
Anaerobic Decomposition

Anaerobic decomposition can be used on ranches and livestock farms in addition to landfills. Manure and other animal waste can be processed through anaerobic decomposition to meet the farm’s energy demands sustainably.

Also read: Wind Energy: Definition, Advantages, and Future

Advantages of Biomass Energy

Here are the major advantages of biomass energy that has made it a global player in the renewable energy sector:

  • Biomass is a sustainable energy source that is both clean and efficient.
  • The sun provides the initial energy, and plants or algae biomass can regenerate in a relatively short period. Hence it is a renewable source of energy.
  • Trees, crops, and municipal solid waste, which are the feedstock for biomass energy production, are all accessible regularly.
  • When we sustainably grow trees and crops, they can help to offset carbon emissions by absorbing CO2 through respiration. The quantity of carbon reabsorbed in some bioenergy processes even exceeds the amount of carbon produced during fuel processing or use.
  • We can collect many biomass feedstocks, such as switchgrass, on marginal lands or pastures without interfering with food crops.

Disadvantages of Biomass Energy

While biomass has various advantages, it is not an ideal energy source. We must examine its drawbacks as well which are as follows:

  • Water makes up to 50% of the biomass, which escapes throughout the energy conversion process. Hence the “energy density” of biomass is lower than that of fossil fuels.
  • According to scientists and engineers, transporting biomass more than 160 kilometers (100 miles) from its processing point is not cost-effective. However, turning biomass into pellets (rather than wood chips or larger briquettes) can boost the energy density of the fuel and make it easier to transport.
  • To grow the materials used in biomass energy, we require a vast area of space. This space will not always be available, especially in densely populated places such as cities.

Biomass Energy Future

Energy crops must be grown in vast quantities, requiring large swaths of land, if biomass is to make a significant dent in the usage of fossil fuels. Furthermore, biomass energy must be cost-competitive with conventional energy sources and biological carbon sequestration. If we can cultivate biomass in huge amounts at cheap cost along with research, development, and early deployment of “clean coal” technologies we could lower the cost of converting biomass to electricity and liquid fuels.

Conclusion

Biomass energy has emerged as a frontrunner as a viable alternative to fossil fuels as the search for alternatives to fossil fuels continues. It is a carbon-neutral fuel source with lower costs than fossil fuels and a wide range of applications.

However, several challenges are preventing it from becoming more widely adopted. More needs to be done, in particular, to address the issue of fuel efficiency, as well as challenges such as space and cost. The utilization of biomass energy, in particular, on a home and local level, can result in lower energy bills.

Do you have any thoughts on biomass energy and its prospects? Please share your thoughts in the comments section below.

Fuel Cells- Definition, Advantages and Future

Fuel Cells is a hot topic among scientists these days thanks to their wide range of applications. Their uses are so diverse that fuel cells have found a place even in the space program. In this blog, let me explain in detail the design, working, types and future scope of fuel cells.

Shall we begin?

What are Fuel Cells?

Fuel cells are electrochemical cells that use a pair of redox reactions to transform the chemical energy of a fuel (typically hydrogen) and an oxidizing agent (usually oxygen) into electricity. It finds various applications, including transportation, industrial/commercial/residential structures, and long-term grid energy storage in reversible systems.

Fuel cells are unique in that they may use a wide range of fuels and feedstocks and can power systems as large as a utility power plant and as small as laptop computers. Now, we are moving on to the design of fuel cells.

Also read: Solar Energy- Definition, Advantages, and Future

Fuel Cells Design

A fuel cell comprises 3 adjacent segments namely the anode, the electrolyte, and the cathode. At the intersections of these segments, redox reactions take place. Fuel is burned, water or carbon dioxide is produced, and an electric current is produced, which can be utilized to power electrical devices, commonly referred to as the load.

A fuel cell’s design elements include:

  • An electrolyte – It acts as a medium of transport between the electrodes. Most common electrolytes include potassium hydroxide, salt carbonates, and phosphoric acid, and it usually defines the type of fuel cell.
  • A fuel – The fuel undergoes oxidation reaction and supplies the ions. Hydrogen is the most common fuel.
  • Anode Catalyst – It breaks down the fuel into electrons and ions. We usually use fine platinum powder as the anode catalyst.
  • Cathode catalyst – It reacts with the ions that reach the cathode and transforms them into harmless compounds, the most common of which is water.
  • Gas diffusion layers that are resistant to oxidation.

Let me show you how fuel cells produce electricity from the fuel we supply.

Fuel Cells Working

In 1839, Sir William Robert Grove, a physicist invented the first fuel cell. The goal of a fuel cell is to generate an electric current that can do some work outside of the cell, such as powering an electric motor or lighting a city.

A catalyst at the anode promotes oxidation reactions in the fuel. As a result, hydrogen atoms are stripped of their electrons at the anode of a fuel cell. The hydrogen atoms have now become positively charged H+ ions.

At full rated load, a typical fuel cell produces a voltage of 0.6 to 0.7 V. If we require alternating current (AC), we must channel the DC output of the fuel cell via a conversion device called an inverter.

Reactions inside Fuel Cell

When the ions and electrons reach the cathode, they rejoin, and the two react with a third molecule, usually oxygen, to produce water or carbon dioxide. The following are the basic reactions that take place inside a fuel cell:

Anode side:  2H2 => 4H+ 4e–  

Cathode side: O2+ 4H++ 4e=> 2H2O

Net reaction: 2H2 + O2 => 2H2O

Fuel cell reaction

Different types of fuel cells

Depending on the electrolyte in use, there are different types of fuel cells. Here are some of them:

Alkali Fuel Cells

  • Alkali fuel cells use compressed hydrogen and oxygen to function.
  • Their electrolyte is usually a solution of potassium hydroxide (chemically, KOH) in water.
  • The efficiency is around 70%, and the operating temperature is between 150 and 200 degrees Celsius (about 300 to 400 degrees F).
  • The output of the cells ranges from 300 watts (W) to 5 kilowatts (kW).
  • However, they require pure hydrogen fuel, and their platinum electrode catalysts are costly. They can also leak, just like any other liquid-filled container.
  • In the Apollo spacecraft, alkali cells were employed to produce both electricity and drinking water.

Molten Carbonate Fuel Cells

  • The electrolyte of molten carbonate fuel cells (MCFC) consists of high-temperature salt carbonates (chemically, CO3).
  • The efficiency ranges from 60% to 80%, and the working temperature is around 650°C (1,200 degrees F).
  • The high temperature prevents the poisoning of cell by carbon monoxide, and waste heat can be recycled to generate more energy. However, the high temperature limits the materials and applications of MCFCs–they are likely too hot for domestic use.
  • In addition, the processes consume carbonate ions from the electrolyte, necessitating the injection of carbon dioxide to compensate.

Also read: Tidal Energy – Definition, Advantages, and Future

Phosphoric Acid Fuel Cell

  • The electrolyte of PAFCs is phosphoric acid, which is a non-conductive liquid acid that causes electrons to go from anode to cathode via an external electrical circuit.
  • Since the anode’s hydrogen ion generation rate is low, we use platinum as a catalyst to boost the ionisation rate.
  • The use of an acidic electrolyte is a major disadvantage of these cells. This accelerates the corrosion or oxidation of phosphoric acid-exposed components.
  • The operating temperature is between 150 and 200 degrees Celsius, and the efficiency ranges from 40 to 80% (about 300 to 400 degrees F). Phosphoric acid cells now available have outputs of up to 200 kW.

Solid Oxide Fuel Cells

  • Solid oxide fuel cells (SOFC) use a hard, ceramic composition of metal oxides such as calcium or zirconium as an electrolyte.
  • The efficiency is around 60%, and the output of the cells can reach 100 kW.
  • The working temperature is around 1,000 degrees Celsius (about 1,800 degrees F).
  • Further energy generation through waste heat recovery is possible. The high temperature, on the other hand, limits the applications of SOFC units, which are typically quite big.

Let’s have a look at the different applications of fuel cells.

Fuel Cells Applications

Fuel cell technology has a variety of applications. Currently, scientists are carrying out extensive research to develop a cost-effective fuel cell-powered automobile. The following are a few examples of the uses of this technology:

  • Fuel cell electric vehicles, or FCEVs, use clean fuels and are thus more environmentally benign than vehicles powered by internal combustion engines.
  • Many space voyages, like the Appolo space program, have relied on them for power.
  • In many rural regions, fuel cells are a major backup source of electricity.

Also read: Wind Energy: Definition, Advantages, and Future

Fuel Cells Advantages

Fuel cells outperform traditional combustion-based technologies, which are now in operation in many power plants and automobiles. They emit fewer greenhouse gases and zero atmospheric pollutants that contribute to smog and health issues. When pure hydrogen is the fuel, the only byproducts are heat and water. Traditional combustion systems use significantly more energy than hydrogen-powered fuel cells.

Fuel Cells Future

Hydrogen is the most abundant element in the universe, and a hydrogen ecosystem focusing on fuel cell technology has enormous promise. Unlike batteries, we can scale up fuel cell technology for passenger vehicles, buses, ships, and trains. Hydrogen will also power urban air mobility in the future.

Fuel cells could power our cars in the future, with hydrogen replacing the petroleum fuel currently used in most vehicles. Many automakers are investigating and developing transportation fuel cell technologies. Hyundai is pioneering hydrogen fuel cell technology in addition to increasing its array of battery, hybrid, and plug-in electric vehicles.

Shall we wrap up?

Conclusion

Due to its non-polluting nature and a vast range of applications, the future looks bright for fuel cells. Once we are able to cut down the cost of fuel cells and devise methods for the safe and long term storage of hydrogen, fuel cells would revolutionize the energy sector.

In case of any queries, please feel free to ask in the comments section. Happy Learning!

Sustainable Waste Management – Full Details

Sustainable Waste Management has become the need of the hour with the ever-increasing amount of garbage that humans generate. According to the United Nations, around 11.2 billion tonnes of solid garbage are collected worldwide, with humans accounting for nearly all of it. As a result, we must devise plans for long-term sustainable waste management.

In this blog, we will discuss the importance of sustainable waste management, its importance as well as the ways of doing so. Let’s get started with the definition of sustainable waste management.

What is Sustainable Waste Management?

Sustainable waste management refers to the collection, transportation, valuation, and disposal of different types of garbage in a manner that does not damage the environment, human health, or future generations. It encompasses all activities involved in waste management, from production to final treatment.

Sustainable waste management aims to limit the amount of natural resources utilised by

  • reusing as much natural materials as possible
  • producing as little garbage as possible.

A well-functioning sustainable waste management system should have feedback loops, a process-oriented approach, adaptability, and methods for waste diversion. It is critical to adhere to environmental sustainability in this regard so that we can manage all the garbage efficiently rather than dumping it in landfills.

Also read: Land Pollution Effects – Top 7 Effects Explained

Why Sustainable Waste Management Is Important?

Let’s have a look at the importance of sustainable waste management and what makes it an attractive option.

Creates space

In the absence of a proper waste management system, garbage will end up on land, either scattered or centralised in a landfill. Landfills are large structures that take up a lot of space. Densely populated cities can’t afford a lot of space for the sake of landfills.

In such cities, we have to manage and sustainably control our waste so that we can dispose of it properly without wasting space for landfills. Before you move to the next section, make sure that you check out Landfills – Causes, Operation and Life Cycle- Everything you should know

Sustainable waste management Saves and also makes money

Recycling more can help us save money since we will not need to buy another identical item once we have reused or recycled it. Sustainable waste management, in line with the concept of money, can assist some businesses in generating revenue.

Municipalities that collect garbage, for example, might charge collection and recycling fees, gaining money in the process. This will also deter institutions that generate a lot of waste, making them more sustainable and environmentally conscious.

Prevents Pollution

Each type of rubbish we dump has a unique impact on the ecosystem. Pharmaceutical waste, for example, contaminates our water, and discarded meals attract flies and rodents. To avoid this, we should return pharmaceutical waste to the manufacturer for proper disposals, such as burning. Food waste can be sent for composting and plastics for recycling.

All of these measures, as well as others, will aid in pollution control. As a result, pharmaceutical waste won’t pollute the water, plastics won’t block marine life, and food waste won’t attract mice. Sustainable waste management enables us to better understand our garbage and how to manage it.

Also read: Land Pollution Causes -Top 6 causes explained

Waste Management Hierarchy in Sustainable Waste Management

The waste management hierarchy is the foundation for sustainable waste management. It focuses on

  • Avoidance
  • Reduction
  • Reuse and recycle
  • Energy recovery
  • Treatment or disposal

Its goal is to prioritise behaviours that maximise resource efficiency, with renewable and less wasteful methods at the top of the pyramid. We’ll look at how the waste management hierarchy is crucial to long-term waste management in the upcoming section.

Reduction and avoidance

The primary aim is to avoid and reduce the amount of waste produced. This can be accomplished by increasing efficiency while lowering consumption. To begin with, businesses and consumers should select products that take the least amount of resources to manufacture including the packaging.

Additionally, wherever possible, we should abstain from using single-use or disposable commodities. These materials form the core of linear waste, in which resources are harvested, processed, and redistributed only to be discarded.

3R concept
3R concept

Reuse and Recycle

If we cannot avoid the consumption of a product then we should choose things that are reusable. Also, we should promote awareness on how to reuse waste products. Processing new materials require money, energy, and often other resources. Since reusing helps us to save these resources, we prefer it over solutions lower down the hierarchy.

One of the core aspects of the zero-waste concept is reuse, which can take the form of having shoes repaired, giving clothes and objects for others to use, and even finding recipes for food leftovers rather than tossing them away. If an object cannot be reused, recycling is the next best choice.

Recycling is suitable for materials that have reached the end of their usable life in their existing form. It minimises the need to extract virgin resources and mitigates some of the negative consequences of waste disposal. Recycling is less desirable than reusing and reducing because it needs more energy, money, and resources to convert the garbage into useable products.

Energy Recovery

Energy recovery is the next stage, which involves converting waste into useable heat, power, or fuel, such as biogas. This is accomplished using a variety of techniques such as

  • Incineration (with energy recovery),
  • Gasification
  • Pyrolysis
  • Anaerobic digestion
  • Landfill gas (LFG) recovery

Combustion is a typical technique of energy recovery for non-hazardous waste. and while it is less favourable to reuse or recycle, it helps lower the physical volume of waste transported to landfills and also produces energy from the burning process that would otherwise require fossil fuels.

Treatment or Disposal

Treatment or disposal is the final and least desirable step in the hierarchy. This usually refers to landfills or incinerators that do not recover energy. Some waste demands treatment but we should avoid it as much as possible by using sustainable waste management techniques.

Sustainable Waste Management Solutions

What criteria must professionals and citizens use to decide if waste management procedures are “sustainable?”

Fundamentally, building a circular economy of waste, as opposed to the make-use-dispose paradigm, is crucial to sustainable waste management. In a circular economy of waste, it returns as a new product or source of energy in a sustainable manner.

Solutions for long-term waste management include:

Composting

Composting is a green and environmentally friendly technique to dispose of waste. Common household items that can undergo composting include excess fruits, tea bags, eggshells, coffee filters, etc. Since it will nourish the soil, the compost pit will be an excellent addition to your workplace or home garden.

To keep odours and fruit flies at bay, tightly close the composting bin or bag. In general, composting converts and recovers organic matter into stable, sanitary, and soil-like products that are high in humic chemicals that replenish the soil.

composting
composting

Avoid Single-use products


We must promote reusable products instead of single-use ones. Get mugs or glasses instead of cardboard coffee cups. Even at professional composting facilities, many supposedly green things, such as compostable coffee cups, don’t undergo composting. They eventually end up in landfills. If we can switch to a greener option like glass which we can reuse and recycle it could save both the environment and money.

Make the switch to digital.

Paper and paper products account for the majority of Municipal Solid Waste. Switching as much paperwork as possible to digital forms is a simple strategy for organisations to improve sustainable waste management. This includes

  • Sending and receiving bills electronically rather than in paper
  • Keeping meeting minutes in a shared document rather than printing them
  • Converting to online banking

Conclusion

If the correct framework is in place, waste management can be sustainable in both enterprises and homes. But, more importantly, the implications of ignoring waste are just too serious to ignore. So, let us join our hands to manage waste, adopt sustainable waste management solutions into our day to day life and convert waste into a resource.

Happy Learning.