Animal wastes are classified as solids, slurry, or wastewater in shape of feed or residues, effluents, hatchery, refuse, slaughterhouse waste and manure. An estimate of 335 million tons of dry waste is produced annually on Animal farms in the United States, representing almost a third of the total municipal and industrial waste produced every year. Biogas from animal manure through anaerobic digestion is an effective way to produce renewable energy while simultaneously reducing greenhouse gas emissions and managing waste.
Animal wastes contain potential ingredients like high Nitrogen, Phosphorus, and organic contents in the forms of residual feed and animal excreta that can cause severe pollutions to the environment if left untreated.
On the other hand, the substances in animal wastes still store a great amount of energy that can be recycled to produce electricity, Biogas, fertilizers, soil amendments, microbial fuel, bioplastics and fertilizers.
By recycling organic wastes into renewable energy and soil products, Biogas systems help offset emissions, enhance sustainable environment, protect our air, water, and soil and reduce greenhouse gas emissions.
Biogas systems recycle all this material and help produce renewable energy and soil products which displace fossil fuels. By this, we can prevent tons of carbon emissions from entering our air, prevent nutrients from entering our waterways, create healthier soils with natural, non-fossil fuel-based fertilizers, and produce reliable and renewable energy.
What is Biogas
Biogas is produced when organic materials (plant and animal products) are broken down by bacteria in an oxygen-free environment, a process called anaerobic digestion. Biogas systems use anaerobic digestion to recycle these organic materials, turning them into biogas, which contains both energy (gas), and valuable soil products (liquids and solids).
Biogas contains roughly 50-70 percent methane, 30-40 percent carbon dioxide, and trace amounts of other gases. The liquid and solid digested material, called digestate, is frequently used as a soil amendment.
Organic wastes also generate large amounts of Methane as they decompose which is a powerful greenhouse gas that traps heat in the atmosphere more efficiently than carbon dioxide. Methane (CH₄) emissions in the United States were equivalent to 761 million metric tons of carbon dioxide (CO₂) equivalent in 2022 becoming the third-largest methane emitter worldwide.
Methane absorbs 86 times more heat than carbon dioxide. To reduce greenhouse gas emissions and the risk of pollution to waterways, organic waste can be used to produce biogas, a renewable source of energy. Sometimes, when displacing fossil fuels, biogas reduces these emissions resulting in carbon negative systems.
American Biogas Production – an Overview
Biogas systems are a potential solutions to address the United States need to manage millions of tons of food, water and animal waste. They also prevent tons of carbon-related emissions from entering the air, keep nutrients from polluting waterways, create healthier soils with natural, non-fossil fuel-based fertilizers, and produce reliable renewable energy.
After processing, biogas is most often used as a renewable substitute for natural gas, electricity and heat with a carbon intensity of 50% to 700% less than fossil fuels.
U.S. has approximately 2,300 sites producing biogas in all 50 states representing an estimated $37.5 billion of capital investment representing numerous potential benefits of organic waste utilization, including environmental protection, investment and job creation. In 2023, 96 new biogas projects became operational in the U.S., pushing the total number of active U.S. biogas projects to around 2300.
These new projects produce 66,000 standard cubic feet per minute (SCFM) of biogas, or an electricity equivalent to 4,000 football fields of solar panels, or powering 600,000 homes, or the fuel equivalent to eliminating 600,000 gasoline cars from the road.
C2e Renewables in Warsaw, North Carolina is the largest utility-scale biogas plant in the United States which produces enough biogas to generate 290 gigawatt hours of electricity per year, enough to power 32,000 homes. The plant Processes more than 750,000 tons of organic waste annually.
Keeping in view the future needs, there is a potential of developing more 15,000 new sites in dairy, poultry, and swine farms, water resource recovery facilities, food scrap-only systems. If it is fully realized, these new biogas systems could produce 103 billion kilowatt hours of electricity each year and reduce the emissions equivalent of removing 117 million passenger vehicles from the road.
Apart from above, The United Nations has the vision 2030 agenda for sustainable development encouraging countries to adopt sustainable production practices, conduct scientific research, and employ appropriate technologies as well as management methods to reduce the greenhouse gas emissions (GHG emission).
How Bio gas is Produced?
The biogas production process is called anaerobic digestion, and it is less harmful to the environment than the processes that use fossil fuel. Here, the bacteria break down organic matter in the absence of oxygen, a phenomenon we sometimes refer to as decomposition or fermentation.
The decomposition goes through 4 stages to turn the organic material into biogas. First, bacteria break down carbohydrates, then acidogenic bacteria turn sugars and amino acids into carbon dioxide, organic acids, hydrogen, and ammonia.
In the third stage, these organic acids are transformed until methanogens can finally break the components in the fourth stage and obtain methane and carbon dioxide. The average energy potential gets close to 2 Gigajoules (1,895,634 BTU) per ton of waste.
This process occurs naturally in swaps and at the bottom of the oceans, rivers, or lakes where organic residues transform into anaerobic conditions. However, it can easily be replicated in artificial environments called digesters.
Digesters are engineered containers that provide an oxygen-free space where bacteria can freely do their job where waste is kept inside the digester, then bacteria starts breaking down the organic components and turn them into biogas as a liquid (between 30 and 60 percent of the input), digestate, and pruning residues.
The digestate and pruning residues become compost and can be repurposed as fertilizer. It is a Zero-Waste process that enables us to obtain energy and heat from sustainable sources while also producing natural fertilizer.
The natural fertilizers however have their own potential benefits for the human and the environment and we get better crops with no need for unhealthy, chemical substances.
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| Image: A Conventional Biogas Plant (Digester) for residential needs |
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| Image: Integrated Biogas System |
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| Image: Biogas Digesters for Commercial Production |
Global Biogas Production - an Overview
Globally, there are 132,000 small to large scale biodigesters and around 50 million operating micro-scaled biodigesters that are primarily used for heating or cooking.
The International Renewable Energy Agency (IRENA) today shows that, in 2023, there was a record deployment in the power sector by reaching a total capacity of 3,870 Gigawatts (GW) globally through renewables including a 21,385 Megawatt from Biogas.
Renewables accounted for 86% of capacity additions indicating a trend far from the tripling renewable power target by 2030.
This demonstrates a phenomenal growth trend in renewable energy including biogas production via anaerobic digestion. The anaerobic digestion system has the potential to generate 10,100–14,000 Tera Watt-hours of energy, which is equivalent to 6–9% of global primary energy consumption.
Environmental benefits of Biogas
- Recycling the manure kills odors and pathogens along-with producing renewable energy and soil products.
- Moving manure from landfills to an airtight biogas system reduces GHG emissions.
- Reduces carbon emissions in transportation by at least half as compared to fossil fuels.
- The use of digestate can replace costly synthetic fertilizers and can increase plant growth by 10-30 percent as compared to synthetic fertilizers.
- Plants absorb soil nutrients, like nitrogen or phosphorus, more easily than raw manure. This allows farmers to minimize the additional cost of synthetic fertilizers.
Energy Benefits of Biogas
- Biogas systems support typically localized power generation plants which results in lower transmission cost.
- Systems with gas storage can provide renewable electricity on demand in lesser time, reducing the need to turn on fossil fueled power plants to meet peak demand.
- Biogas can be used interchangeably with natural gas for heating, electricity, and the production of quality biomethane and transportation fuel.
- The thermal heat needed in industrial manufacturing is responsible for around 11% of U.S. emissions. Biogas is currently the most sustainable way to address these emissions.
Conclusion
US spends millions of US$ each year to transport millions of tons of waste to incinerators and landfills. Diverting that waste to anaerobic digestion systems, especially localized Biogas plants would turn this waste to generating revenue from energy production and co-products.
These systems also supports famers to reduce their farm costs for animal bedding and fertilizers adding to their revenue streams. There is a potential of developing more such facilities in US and worldwide for sustainability of natural wastes to protect the environment and human health.
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