Alternative Engery: Biogas

Biogas, also known as biomenthane, swamp gas, landfill gas, or digester gas, is produced through the anaerobic digestion (fermentation) of decaying plant or animal matter. It is the naturally occurring emission of bacteria that thrive without oxygen, and occurs in three steps. First is the decomposition, or hydrolysis, of the biodegradable material into molecules such as sugars. Next, these molecules are converted into acids. Lastly, the acids are converted into biogas. Anaerobic digesters harness the bacteria’s natural processes to capture and utilize the biogas, all in a safe, controlled environment.

Biogas can be produced from a wide variety of available organic materials and wastes, including sewage sludge, animal manure, municipal/industrial organic waste, stillage from ethanol production, crop residues, and specially grown energy crops.

Normally, they take these products and make fertilizer and the gas is just byproduct that is released. But if we obtain the fuel first, we can prevent runoff and methane emissions. Then the residue created by the burning of biogas can be dried and used as fertilizer.

http://www.lowimpact.org/factsheet_biogas.htm

Landfills are the third-largest source of human-related methane emissions in the United States. Methane can be captured from landfills and used to produce biogas. Methane gas collection is practical for landfills at least 40 feet deep with at least 1 million tons of waste.

The U.S. Environmental Protection Agency (EPA) estimates 8,200 U.S. dairy and swine operations could support biogas recovery systems with the potential to generate more than 13 million megawatt-hours and displace about 1,670 megawatts of fossil fuel-fired generation collectively per year. Biogas recovery systems are also feasible at some poultry operations.

I love this idea. As gross and unsanitary as it sounds, biogas would be our solution to both our problem of needing a renewable energy and it helps solve our huge waste problem. Before I get too excited, let’s look at the specifics.

Biogas is usually 50% to 80% methane and 20% to 50% carbon dioxide with traces of gases such as hydrogen, carbon monoxide, and nitrogen. In contrast, natural gas is usually more than 70% methane with most of the rest being other hydrocarbons (such as propane and butane) and traces of carbon dioxide and other contaminants.

When cars burn gasoline it produces carbon monoxide, nitrogen oxides, the main source of urban smog, and unburned hydrocarbons, which is the main source of urban ozone.

Carbon is also a problem. When it burns, it turns into lots of carbon dioxide gas. Gasoline is mostly carbon by weight, so a gallon of gas might release 5 to 6 pounds (2.5 kg) of carbon into the atmosphere. The U.S. is releasing roughly 2 billion pounds of carbon into the atmosphere each day.

www.science.howstuffworks.com/gasoline.htm

Compressed biogas (CBG) is the most climate friendly of more than 70 different fuels and is considered to be CO2 neutral.

And since the conversion process in the digester is anaerobic (it occurs in the absence of oxygen), it destroys most of the pathogens present in dung and waste, thereby reducing the potential for infections like dysentery and enteritis.

The burning of traditional fuels like dung cakes or wood (this article was written about India. That is why they say dung is a traditional fuel) releases high levels of carbon monoxide, suspended particulates, hydrocarbons, and often, contaminants like sulfur oxides. Because it is a gas, biogas burns much more efficiently than these solid fuels. It leaves very few contaminants, although it is true that biogas releases small quantities of sulfur oxides. Biogas offers perhaps the most environmentally benign method for tapping the solar energy stored in bio-mass. It’s a renewable and decentralized alternative to the other methane-based fuel, natural gas, which is commonly used in cities.

Methane, which I talked about in my landfill effects post, is explosive if it isn’t burned. (I saw this when I was working on my summer class project. My video was already way too long, so I didn’t add the stuff about methane and leachate, but here is a picture).

Methane

Sorry about the poor picture quality, but that small flame in mid-left side of the picture is the burning methane. It’s bigger in real life, but still pretty cool.

This stuff could be used, but usually it is just burned, so it’s just wasted.

Biogas reduces emissions by preventing methane release in the atmosphere. Methane is 21 times stronger than carbon dioxide as a greenhouse gas. It also saves money because it means that landfills don’t have to worry about complying with EPA combustion requirements. Producing biogas through anaerobic digestion reduces landfill waste and odors, produces nutrient-rich liquid fertilizer, and requires less land than aerobic composting.

http://www.faculty.fairfield.edu/faculty/hodgson/Courses/so191/SouthAsReadings/IndiaEnergySuccess.html

http://www.bioprocesscontrol.com/templates/standard.aspx?pageId=34

http://www.nrdc.org/energy/renewables/

http://www.afdc.energy.gov/fuels/emerging_biogas.html

As far as cons go, when it is compared to gas, it doesn’t seem like a bad solution. I didn’t find any talk about animals or habitats being affected, so that’s always good. But there wasn’t a whole of information on this subject, in general, so it may not be popular enough to have a whole lot of research.  If not monitored responsibly, some problems could arise though.

Biogas can accumulate under roofs and ceilings. Carbon Monoxide gas can gather in engine exhaust and poorly operating boilers. And hydrogen Sulfide gas, which can collect in the bottom of tanks and pump sumps, can kill almost instantly.

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2 responses to “Alternative Engery: Biogas

  1. Hi! Serendipitousscavenger. Don’t ask me to pronounce that! You have done a lot of research I can see, in order to write this. I think that the only way that animals or habitats would be affected would be if and AD Plant was built on their land. The natural world does benefit from the digestate which if used as a fertilizer is much more natural than chemical fertilizers. One asset which is little spoken of but is massive, is that the AD digestate increases baxteriological activity in the soils and this alone boosts plant health and tolerance to disease and drought.

    Thanks.

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