Explaining biogas

In a nutshell, biogas is a renewable form of energy that can be combusted to produce electricity, or directly to produce heat in the form of a flame. It can also be used as a fuel for certain kinds of vehicles, as well as having wide-ranging commercial, industrial and domestic applications. While biogas might not be the first thing that comes to mind when considering renewable, green energy, it is actually considered environmentally friendly and sustainable.

Many homes in the UK and across the world depend on biogas for heating, cooking, and other domestic tasks, and this kind of fuel has replaced much of the use of fossil fuels such as coal and gas, particularly in power stations. In the UK, around 43% of our power still comes from the burning of fossil fuels, while 37% comes from renewable sources including natural gas. The benefit of using biogas as a fuel is that it burns much more cleanly than fossil fuels do, creating lower levels of carbon dioxide emissions and less particulate matter that can cause respiratory problems among the population.

What is biogas made up of?

When looking at the chemical composition of biogas, it is noted that the specific composition can vary depending on several factors, including the nature of the raw materials used in its production. These variations tend to be relatively minor, and generally speaking biogas is made up of mostly methane, with some carbon dioxide in the mix. Biogas also contains other compounds and elements in small quantities, such as hydrogen sulphide, nitrogen, ammonia, and siloxanes. Methane is the combustible component of biogas and it is what makes it such an efficient fuel.

Biogas is very similar in composition to natural gas and is used in much the same way. This gas can be cleaned up and filtered to meet the standards expected of natural gas, and this means the two can be used interchangeably. Once biogas has undergone this cleaning process it is often called biomethane to distinguish it from untreated biogas.

Where does biogas come from?

Biogas is the product of biological processes, namely the anaerobic bacterial decomposition of cellulosic or organic matter. In an enclosed, oxygen-free environment, methanogens, which are methane-producing microorganisms, break down organic matter and produce methane and other organic compounds as byproducts. An example of this process taking place on a large scale can be seen in landfills, where commercial, industrial and domestic waste is packed into a sealed environment and the decomposition of the organic matter is allowed to accelerate over time.

How long does it take to produce biogas?

There is no single answer to the question of how long does it take to produce biogas. Plants that produce biogas with a view to harvesting and processing it to be sold as a fuel will accelerate the decomposition process artificially by using something called a digester, as part of an anaerobic digestion project. When operating a digester at 37 degrees celsius and mixing the waste, the process can take as little as 30 days. In a less highly controlled environment such as a landfill, biogas production can take much longer.

In the landfill setting it is harder to create an oxygen-free environment, so before methane production can take place, aerobic bacteria must first use up all of the available oxygen within the waste. Generally speaking, it takes about a year for this stage to be completed, and once it is complete methane production can begin. Of course, landfills tend to be outdoors so the ambient conditions can affect the rate at which deoxygenation is complete and methane production begins. Warmer, more humid conditions will lead to faster decomposition, whereas cold, dry conditions will slow it.

Monitoring methane and biogas emissions

Global governments should support methane monitoring and measurement efforts in order to meet goals relating to climate change and pollution. The data from these monitoring programs can help identify gaps in the current measurement portfolio and identify super-emitters and unaccounted sources. Moreover, international agencies should support the efforts to develop and implement an interagency scientific working group to compare current and future activities to strategic policy objectives. This will help ensure that the efforts to mitigate climate change are concerted and optimised.

While there are many advantages to methane monitoring, it can be a challenging process. For instance, the results are not always reliable because of the time and distance involved in taking the measurements. Fortunately, the latest technology helps us to monitor the emissions in a safe, accurate and reliable manner. With real-time data, it is possible to compare the methane emissions from the different sources in a region, allowing us to compare them and assess them against the levels of methane in the atmosphere nationally and globally.