When microscopic anaerobic bacteria digest their dinners, they emit a hodgepodge of gasses, mostly methane and carbon dioxide. That gaseous potpourri is biogas, and clever engineers think that it’s the ticket to transforming organic waste into usable energy. How, you ask? Well, if you toss and turn at night, watching hydrocarbon chains dance like sugar plums in your head, wondering how biogas works, then read onward.
What Is Biogas Energy?
Biogas is a type of biomass energy, the mixture of gasses produced when anaerobic organisms consume organic. It is not “organic” as in USDA-certified, but as in made by nature – biodegradable material in the absence of oxygen. The mixture is primarily methane and carbon dioxide.
In general, the higher the temperature and the less oxygen, the more methane produced, up to 55-60 percent by volume. Biogas hails from several sources: Municipal Solid Waste (MSW) landfills, agricultural waste digesters, and waste resource recovery and treatment plants.
How Does Biogas Energy Work?
In its raw form, biogas is a combustible, smelly, gaseous stew with trace amounts of hydrogen sulfides, siloxanes, and other chemicals. It comes mostly from fatty, oily and greasy substances (FOGs) and organic waste high in nitrogen and carbon. Popular sources include animal manure, meat trimmings, yard trimmings, food waste, human sewage, etc. “Woody wastes do not digest well because their strong fibers are naturally resistant to degradation,” reports the American Biogas Council. Other plant-based fibrous materials, such as cardboard and cotton, take longer to digest as well. Inorganic materials, such as glass, metal, ceramics, stone, plastic, cannot be anaerobically digested.
Here are the steps to turning biogas into energy:
1. The waste and feedstock are collected in an aerobic container. Large-scale projects heat or cool the container to maintain the temperature at 86 to 100 degrees Fahrenheit to accelerate bacterial activity.
2. The feedstock receives vitamins, supplements, and possibly water to adjust its chemical composition to achieve maximum methane production and minimal toxins.
3. An extraction system collects the resulting gas. Since the gas is naturally lighter than solids and liquids, it rises to the top of its container.
4. The biogas is refined for further use. It may be upgraded to the same quality as medium-BTU or high-BTU natural gas and piped into liquid (LNG) or compressed (CNG) natural gas pipelines. It may be used for direct heating, such as a boiler or furnace, or it may be used as fuel in an internal combustion engine or steam-driven turbine to generate electricity.
Key Advantages of Biogas Energy
Biogas is a net-carbon-neutral technology, according to the Environmental Protection Agency (EPA), because it absorbs and releases carbon in a cycle. Carbon dioxide is absorbed by plants by means of photosynthesis and released during combustion or digestion. At the end of the day, biogas energy contributes nothing to global warming.
2. Nutritious Fertilizer
The feedstock in an anaerobic container is not all converted to gas. The remaining sludge is a strange sort of composted organic stew, pure gold for agriculture. “Other byproducts of biogas systems include non-energy products such as nutrient-rich soil amendments, pelletized and pumpable fertilizers, and even feedstock for plastics and chemicals,” reports the EPA.
3. Worldwide Resource
Waste – food rubbish, animal poop, crop feedstock – is everywhere. Biogas collection can be effectively implemented on medium- and large-scale projects around the nation and around the world. Already, Northern Europe is leading the way in biogas production, with North America coming in second. India and China have employed anaerobic digesters for decades. Currently, biogas generates about five percent of electricity in the United States.
4. Reduces Global Warming Agents
Methane has 26 times more global warming potential than carbon dioxide over a 100-year timespan. In the case of solid waste landfills and other open spaces of anaerobic digestion, the methane would otherwise escape into the atmosphere. Biogas energy collects this resource, transforming it from a dangerous global warming agent into a valuable asset.
5. Better than Composting
An Austrian study concluded that converting the country’s two million tons of biowaste into biogas was a more effective solution than traditional composting. The average net energy gains were 599 kilowatt-hours per ton of biowaste.
6. Natural Gas Substitute
Once cleaned up, biogas can be used as renewable natural gas and piped into the same lines for the same uses. Unlike natural gas, which is usually a byproduct of oil drills in remote regions, biogas can be generated locally and economically.
4 Main Disadvantages of Biogas Energy
1. Risk of Explosion
Methane, by itself, is odorless, colorless and explosive when paired with the right proportions of air. This may cause dangers for maintenance workers when performing field service. Also, due to federal regulations for explosive materials, biogas collection and refinement facilities cost exponentially more than otherwise.
2. Requires Waste Separation
Not all materials can be composted. And certain materials impede proper digestion. Currently, the EPA is not entertaining nation-wide waste separation policies, which makes MSW more difficult to digest. Therefore, most industry growth is expected to come from dairy farms waste water treatment plants and other Big Food sources.
3. Remote Energy Generation
The larger the biogas facility, the more profitable. However, since biogas comes from waste and waste is usually disposed far, far away from metropolitan hubs, the biogas energy must be transported over long distances as well. This increases payback periods and requires larger initial investments.
4. Market Volatility
Biogas competes with natural gas. Currently, natural gas is so plentiful that oil companies often flare the gas rather than capture it. Drive through western Texas at night, for instance, and you won’t need headlights. Just drive by the light of the burning gas flares. Until fossil fuel prices rise, biogas will remain the more expensive alternative.
Will biogas energy replace petroleum? Probably not. Nonetheless, it’s the smartest solution to redeeming the millions of tons of waste produced by first-world countries. Best of all, it contributes not an ounce to global warming.