Christian M. 12 min read

Everything you need to know about biogas!

For many authoritative bodies, including the International Energy Agency (IEA) and the Department for Business, Energy and Industrial Strategy (BEIS), biogas stands as a pivotal energy source in our collective pursuit for net zero.

The benefits of biogas clearly outweigh its drawbacks, enabling us to harness an underutilised resource that already exists in abundance: organic waste!

This comprehensive guide delves into the fascinating world of biogas, a biofuel.

Contents

What is biogas?
How is biogas produced?
What is biogas used in?
What are the benefits of biogas?
What are the challenges of biogas?
What is the future of biogas in the UK?
FAQs
External Resources

What is biogas?

Biogas is a renewable fuel made from the breakdown of organic matter in an environment with no oxygen through a process called anaerobic digestion.

Simply put, biogas is the smelly gas made when stuff like cow poo, farm waste and food leftovers rot inside a bio-digester machine.

The interesting part is that these gases can be captured and used as fuel, pretty much like natural gas.

Interestingly, this biogas is mainly made up of methane (CH4) and carbon dioxide (CO2), which are key greenhouse gases, yet it’s seen as a type of green energy and renewable energy.

It’s renewable fuel because organic waste is an inevitable part of human activities (like farming cows, growing crops, or even going for a poop!).

And it’s green because it uses these greenhouse gases that would otherwise just go into the atmosphere without doing anything useful, like organic waste in landfills. Instead, we can upcycle all of this into energy!

When we burn biogasses with oxygen to extract energy, it actually converts the methane into CO2, a less harmful greenhouse gas with a lower warming potential.

So, biogas is a big win! It helps us use less fossil fuels, manage waste better, and reduce greenhouse gas emissions. That makes it a key player in our fight against climate change and in building a more sustainable world.

How is biogas produced?

Creating biogas isn’t quite as straightforward as harnessing wind or solar energy; it requires its producers to roll their sleeves and collect the raw materials first.

This includes anything from livestock manure to leftover food from our kitchens or the food industry and even agricultural waste like spoiled crops.

What’s crucial is the material’s availability and its energy potential – in other words, how much biogas can we get from letting it decompose?

Once the feedstock is collected, they are introduced to a digester – also known as an anaerobic or bio-digester. Despite its sci-fi-sounding name, it’s just a sealed container that keeps oxygen out, creating the perfect environment for the microorganisms responsible for anaerobic digestion.

Fun fact: these microorganisms are also behind our own ‘biogas’ (i.e. farts). They break down the source material in stages, simplifying the complex organic matter and eventually releasing gasses that can be collected and used.

The final stage is to refine the raw biogas for its intended use, similar to refining petroleum into various fuels. Depending on its purpose, the biogas can be minimally processed for basic heating or more thoroughly cleaned for more sophisticated uses, such as electricity production or fuel for vehicles.

One last thing to note: the leftover solid material in the digester isn’t waste – it’s a valuable by-product called the digestate that can basically enable a farm to go fully organic and abandon chemical fertilisers!

In a circular economy, nothing goes to waste.

What is biogas used in?

Biogas is a high-energy, long-lasting fuel that is very different to most other renewables in the sense that it’s incredibly versatile. It can be used for everything from heating homes to powering vehicles and generating electricity.

On farms, where biogas production is often a straightforward process, lower-grade biogas (which contains a fair share of impurities) is used to heat farmhouses, barns, and even greenhouses, enabling year-round crop cultivation, even in colder months.

But biogas isn’t just for farms; it can also be refined and used as a direct substitute for natural gas heating in buildings. Interestingly, it’s even more efficient when used in conjunction with electricity generation.

This is where the Combined Heat and Power (CHP) process comes in. Biogas fuels a turbine that drives an electric generator; the difference is that the heat produced during combustion is also recovered, making this an incredibly efficient energy solution.

We digress; the electricity generated from this process can be used locally or fed into the national grid, bolstering the overall renewable energy mix.

Businesses that generate their own electricity using biogas can sell it to the grid via the Smart Export Guarantee (which replaced the Feed-in-Tariffs scheme in 2019!).

Lastly, biogas is increasingly being seen as a viable transportation fuel when it can be converted into an upgraded product called biomethane.

Biomethane can be used as a direct replacement for natural gas in vehicles adapted to run on this fuel type (very common in countries like Peru!), effectively reducing their overall emissions as the carbon was never extracted from deep underground.

What are the benefits of biogas?

Biogas boasts many benefits, particularly when contrasted against its carbon-based counterparts, such as fossil fuels. Let’s delve deeper into these advantages:

Making the most out of waste

Fundamentally, biogas is an unavoidable byproduct of organic waste. In areas with a high concentration of such waste, like sewage plants, biogas is essentially being lost to the atmosphere without being used.

Helping the climate out

The process of producing biogas contributes greatly to waste management. It redirects organic waste from landfills, where it decomposes anaerobically and releases potent methane directly into the atmosphere. When sent to biogas digesters instead, this waste transforms into a valuable renewable resource.

The production of biogas mitigates climate change in two ways: it reduces the global warming potential of the otherwise released methane and takes a bite out of the market share of carbon-intensive fossil fuels.

Remember, organic waste is inevitable. Those banana peels and leftovers will decompose somewhere and release methane, so why not harness that process?

No-cost natural fertilizer

In addition to generating energy, the process of creating biogas also leaves behind a nutrient-rich solid residue. This can be used as a natural fertilizer, promoting sustainable agriculture and serving as another carbon sink. Imagine pairing this with agrivoltaics for a completely green solution!

By using this natural fertilizer, we can steer clear of synthetic ones, which promote damaging industrial and agricultural practices and contribute to soil degradation – a significant global environmental concern.

Affordable energy

Recall the recent energy crisis? Those farms and local communities relying on biogas likely felt the crunch less, as they were generating their own fuel from their waste, making them less susceptible to inflation.

Visualize creating electricity from burning your junk mail or recycling old electronics – that’s the power of biogas!

Circular economies

Biogas production fits neatly within the concept of a circular economy, where waste isn’t discarded but instead seen as a valuable resource. This viewpoint fosters sustainable and resilient societies, nudging us closer to achieving the UN’s sustainability goals.

Although it might sound utopian, these kinds of shifts in sectors could potentially trigger a major change in our systems. Concepts like distributed grids and the use of cryptocurrencies are just a few examples of these revolutionary ideas.

Bonus: energy storage

Though it’s not widely documented, biogas could potentially serve as a simple and strategic long-term energy storage solution, much like green hydrogen storage.

Rather than going through a complex hydrolysis process (that produces green hydrogen!), producing biogas is significantly more straightforward. It could even be used for electricity storage, similar to Compressed-Air Energy Storage (CAES) systems.

What are the challenges of biogas?

As with any solution, biogas is not without its challenges…

An imperfect process that is hard to scale

When it comes to large-scale raw biogas production, numerous technical concerns come to the forefront. The composition and availability of the source materials (also known as ‘feedstock’) can vary greatly, making it difficult to control the quality and quantity of biogas produced.

Even on farms, the amount of raw organic matter can fluctuate seasonally, which then makes it difficult to maintain precise control over operating conditions, such as temperature, pH, and feedstock type. Remember, there are entire colonies of microorganisms living inside the digestors, just like we humans don’t like when the conditions change on Earth.

However, in other contexts such as sewage, the feedstock (poop and others) is constant, and the challenges are more a matter of efficiency, energy use (see, for example, using floating solar for sewage processing) and quality control, although populations do grow, and what they throw down the drain does change over time! (Hello, micro-plastics).

For this reason, simpler, low-tech installations are often more suitable for biofuels in places like remote farms, while high-tech biogas setups are reserved for specific contexts.

Environmental concerns

Besides carbon emissions and other gasses that affect local air pollution, biogasses have also faced some environmental concerns regarding how they are sourced.

While the vast majority is indeed sourced as a by-product of existing organic waste, there have been cases where energy crops have been grown with the specific purpose of producing biofuels, including biogas.

The expansion of these projects, which include soybeans, palm oil, and sugarcane, has led to clearing natural habitats, including rainforests, to make way for these crops, contributing to very harmful deforestation in regions like Brazil and Indonesia.

Storage and Transportation

Other challenges include the storage and transportation of biogas. Because it is composed mainly of methane, a powerful greenhouse gas, leakage without utilisation defeats the whole point of harnessing it.

Biogas is also flammable and can even be explosive when mixed with air, making its handling a matter of utmost sensitivity. The good news is that the handling of biogas is quite similar to that of natural gas, where there is much experience.

What is the future of biogas in the UK?

It’s bright – the UK’s climate change commitment to achieve net-zero emissions by 2050 and its focus on circular economy principles all point towards a growing relevance of biogas.

Production is expected to increase as organic waste is increasingly separated from landfill waste. Besides the 500+ plants already in existence, several new plants are being installed across the UK.

There’s also growing recognition of the role biogas plays in agriculture by making waste management a revenue stream or significant cost reductions to the farm’s ops (heating, fuelling vehicles, and even producing electricity).

It serves as a renewable energy source, allowing farms to easily meet their future carbon quotas, while the leftover digestate remnant can be used as an organic fertilizer, potentially earning farms an organic label.

Biomethane (a refined product made from biogas) producers are also receiving direct financial incentives through the Green Gas Support Scheme (GGSS) launched in November 2021 to replace the Renewable Heat Incentive (RHI).

Approved plants receive monthly tariffs to compensate for infrastructure costs and ongoing expenses. These incentives are funded by the Green Gas Levy (GGL), charged to business gas suppliers based on the amount of natural gas in their gas mix.

The 500+ anaerobic digesters producing biogas from farm waste, municipal organic waste, landfill, and sewage benefit from these predecent incentives and showcase the acceptance of biogas in the country.

In this sense, the UK is well positioned for biogas because of its historical relationship with Natural gas, including its existing trillion-dollar natural gas infrastructure of pipes, storage units, and gas boilers that can be rapidly adapted to bio-methane.

The future of biogas in the UK looks promising as it aligns with the country’s ambitious climate goals, offers a sustainable waste management solution, and contributes to a greener, circular economy.

FAQs

Biogas vs biomethane

The short answer is that both are products of anaerobic digestion, with the main difference being that biogas is the raw product, while biomethane is purified to be closer to natural gas (i.e. methane!).

The long answer goes as follows:

Biogas: The rawest gas product typically consisting of 50-60% methane, 30-40% carbon dioxide, and trace amounts of other gases. It’s cheap and readily available, suitable for various applications like cooking, heating, electricity generation, and powering internal combustion engines. However, it has a lower energy density and is largely incompatible with existing natural gas infrastructure.

Biomethane: The purified form of biogas with the removal of carbon dioxide and other impurities, resulting in a gas that is typically over 95% methane. Biomethane closely resembles natural gas and can be used interchangeably in most applications, including injection into the natural gas grid and as fuel for natural gas vehicles. This makes biomethane highly valuable and is why it receives significant government support.

Biogas vs natural gas

Although both are carbon-based gas fuels, they differ greatly in their origin and contribution to climate change.

Natural gas: A fossil fuel extracted from deep underground reserves. Its extraction, processing, and usage emit greenhouse gases that contribute to climate change. It is a non-renewable resource as it takes millions of years to form through geological processes.

Biogas: is derived from the anaerobic digestion of organic waste, such as sewage, animal manure, and food waste. It is a renewable resource as human activities constantly renew organic waste at the Earth’s surface. Biogas helps utilize greenhouse gases that would otherwise be emitted into the atmosphere. This makes biogas both renewable and conceptually carbon-negative.

Biogas vs biomass

The main difference between biomass and biogas is their physical state. Biomass is solid, while biogas is in the form of a gas. Biomass can be considered the rawest form of bioenergy and is more controversial since it involves burning carbon stored in solid form.

Biomass includes wood chips and agricultural residues that can be directly burned for heat or converted into other biofuels, including biogas.

Biogas is a by-product from the anaerobic digestion of digestible organic matter like sewage, food waste and animal manure.

What are the different types of biogas plants?

There are various types of biogas plants, ranging from rudimentary pits lined with plastic and collection membranes to high-tech biomethane plants equipped with cryogenic separation units.

The main takeaway is that raw biogas is derived from a process of anaerobic digestion (AD) technology, with its nuances and optimal setup depending on the feedstock and other local variables.

For example, food waste requires pre-processing to remove packaging, while sewage is regularly processed at high temperatures to eliminate pathogens.

If biomethane is the desired output, biogas is “upgraded” or “purified” using technologies like water scrubbing and pressure swing absorption, which are outside the scope of this article.

What are the different applications of biogas?

Biogas releases energy as heat when burned with oxygen through combustion, just like natural gas.

It, therefore, is useful for the same applications, ranging from cooking, heating, electricity generation, fueling combustion engines, etc.

Its versatility makes it a valuable renewable energy source for various purposes.

What are the environmental benefits of biogas?

Biogas can be viewed as a natural byproduct of organic waste decomposition, which is inevitable for as long as there is a large number of humans living sedentary lives on Earth. Waste is a direct result of humans, and this waste naturally emits greenhouse gases over time, period.

Biogas production is literally the harnessing of these unavoidable gases for useful things such as heating, cooking, etc., which normally require natural gas.

By replacing this fossil fuel and utilizing otherwise unused greenhouse gases, biogas helps reduce carbon emissions and improve waste management.

It ultimately encourages the separation of food waste from general waste, reduces landfill volumes, promotes sewage processing, recycling, and has many other positive effects across supply chains.

What are the challenges of biogas production?

Producing biogas can range from being a straightforward process to a complex operation, depending on the aim.

If this is to produce biomethane to sell to the national gas grid, all the standards and regulations set by Ofgem and other government regulators must be met. In other words, serious investment is required; you can’t just have a DIY project.

Another challenge is achieving economic viability. It is necessary to have a constant supply of feedstock, an adequate plant that includes an AD system and purifier, leak-proof storage, a gas connection to the grid or pre-arranged transportation, and ensure there is a market for the biogas.

Again, it’s a serious endeavour with many technical and social challenges: no one likes having a potentially smelly plant next to their house.

How does biogas compare to other renewable energy sources?

Unlike other renewable energy sources that rely on large-scale Earth processes, such as wind, solar radiation, and water flow, biogas relies on renewable human processes: the generation of organic waste.

Alongside biomass energy, it is one of the few renewables that produce greenhouse gases when energy is extracted from it, which may give the impression that biogas is not as beneficial in combating climate change as the other sources.

However, biogas is technically imperishable, energy-dense, and incredibly versatile, making it suitable for mobile applications, among others.

While it differs from typical “renewables,” as long as it is renewable within a human timescale, it is considered a renewable energy source. It is also green and low carbon. ♻️🌱

What are the safety concerns associated with biogas?

Where to start? The safety concerns associated with biogas are essentially similar to those of natural gas, adding in concerns of pathogens making it out during the handling and processing of the feedstock. Faecal matter from sewage and farm waste are regular attendants of an anaerobic digestor!

Otherwise, the usual concerns remain, including its explosiveness when mixed with air, its corrosiveness and toxicity to humans in high concentrations, including the risk of suffocation.

What are the UK regulations governing biogas?

Biogas involves a long supply chain. Organic material collection and processing. Production of biogas and refinement to biomethane in a plant. Safe storage and transportation, purchased by business gas suppliers and consumers.

Therefore, there are a lot of regulatory bodies acting on the biogas industry, namely:

The essentials: Environmental (EA, EPA, EWA), Planning (local authorities), Health and Safety (HSE).
Feedstock: Animal By-Product regulations.
Storage and Use: Gas Safety Regulations.
Renewable Transport Fuel Obligation
Green Gas Support Scheme (GGSS)
Green Gas Levy (GGL)