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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Landfills: How They Affect the Air

To catch up read: how they affect our land and water.

Air

Landfill is the cheapest way of disposing MSW, but all efforts to get rid of waste pollute the environment to some extent. In landfills the disadvantages are that gases and chemicals are released into the air we breathe. Experiments show that the gases and chemicals released from landfill sites are harmful to animals which common sense would tell us, it’s harmful for us too.

Early landfills were put in convenient locations on the least expensive land. The waste was ‘out of sight out of mind.’ People did not realize that as the waste rots and decomposes, it can release toxic chemicals.

Bacteria
However, there is another problem with landfills, whether lined or not. Bacteria in the soil, break down organic matter in the landfill, such as vegetable peelings. As they do so, they release methane gas. Methane is not a poison, but it has two drawbacks. Firstly, it is a greenhouse gas. It contributes to the greenhouse effect that is causing global warming. Secondly it is explosive. If it seeps from the landfill and finds its way into a building, it can build up unnoticed.

Methane Collection System

Bacteria in the landfill break down the trash in the absence of oxygen (anaerobic) because the landfill is airtight. A byproduct of this anaerobic breakdown is landfill gas, which contains approximately 50 percent methane and 50 percent carbon dioxide with small amounts of nitrogen and oxygen. This presents a hazard because the methane can explode and/or burn. So, the landfill gas must be removed. To do this, a series of pipes are embedded within the landfill to collect the gas.

More recently, it has been recognized that this landfill gas represents a usable energy source. The methane can be extracted from the gas and used as fuel. The extraction system is a split system, meaning that methane gas can go to the boilers and/or the methane flares that burn the gas. The reason for the split system is that the landfill will increase its gas production over time and exceed the capacity of the boilers at the chemical company. Therefore, the excess gas will have to be burned. It is not cost-effective to compress the excess gas to liquid and sell it.

The U.S. Environmental Protection Agency (EPA) has endorsed landfill gas as an environmentally friendly energy resource that reduces our reliance on fossil fuels, such as coal and oil. Landfill gas-to-energy projects are most successful when partnered with mature MSW landfills, as opposed to new landfills or C&D landfills.

There are three basic types of landfill gas-to-energy facilities:

Electric – Landfill gas is used as a fuel to generate electricity at small power plants at the landfill, or at a nearby industry, with the generated electricity delivered to a utility company.

Alternative fuel – Landfill gas is piped to an industrial or commercial facility, where it is used for heating in place of, or in combination with, fossil fuels such as oil, coal or natural gas.

Processed gas – Landfill gas is processed and cleaned to natural gas quality and delivered to transmission pipelines, to be used in normal applications for natural gas.

http://www.interstatewaste.com/index.php/press-room/education/learn-about-landfills/

Landfill gas is still a problem. The Greenhouse Effect is caused by so called ‘greenhouse gases’ in the atmosphere. These gases, such as carbon dioxide, methane, and water vapor have existed naturally for millions of years. The amount of these gases has gradually increased, causing the earth to get warmer.

http://www.dldesign.connectfree.co.uk/quarry2.html

Landfill are a lot nastier than I had previously thought. I can’t believe that people think all this work is easier than just recycling. Recycling may be harder in the short run, but it seems like something that will save us a lot of problems and time in the long run.