At ConsensusPower we are on a mission about community-led access to renewable energy and the Anaerobic Digestion industry stands at the heart of it. To reflect our deep-seated commitment to innovation and regenerative practices, we are delving into a series of conversations with experts in the field to get first-hand insights into opportunities, challenges, in the field know-how and the integral role of technology in unifying these elements.

Expect a variety of content formats from us, where we embark on a journey designed to inform, educate and spread awareness on the importance and workings of Anaerobic Digestion and the key role it plays within the circular production and consumption model for both businesses and their surrounding communities.

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What if you could turn your kitchen scraps, garden waste, or leftover crops into clean and green energy? This isn't a futuristic dream but a practice dating back to 900BC, made possible through anaerobic digestion (AD). 

What is Anaerobic Digestion?

Anaerobic digestion (AD) is a natural process that breaks down organic matter, such as food waste, manure, or crops, in an environment depleted of oxygen. This process produces biogas, a combination of methane and carbon dioxide, and digestate, a fertiliser rich in nutrients. 

The biogas produced by AD can be collected and used in many ways, depending on the quality and quantity of the gas. It can be burned in a boiler or a combined heat and power (CHP) unit to produce heat and/or electricity, or it can be upgraded to biomethane by removing carbon dioxide and other impurities, which can then be injected into the gas grid or used as vehicle fuel. 

The digestate, on the other hand, can be separated into solid and liquid fractions, which can be stored and transported to the fields where they can be applied as fertiliser [1].

How does Anaerobic Digestion Work?

Talking about the Anaerobic Digestion process is easier said than done. Until you get to the final products, biogas and digestate, a long, complex chain of events take place, going through a series of specifications, standards, testing and quality control that have to be met.

If you want to go more in depth on these, I invite you to read our interview with Karim Khan, a former non-executive director of Biogen UK. 

Before we move on to scientific terms that take place at a more granular level of the AD process, it’s important to mention that having the raw organic matter available to get started with the process is a must. This raw matter is often referred to as “feedstock”, and it’s a term commonly used within the engineering fields, for any unprocessed material used to produce something in an industrial process [2].

So where does this raw matter come from? Waste! 

This waste can be obtained from a variety of sources:  

Now, moving onto the chemical side of things, below are the four stages that are carried out by different types of microorganisms that work together to convert complex organic matter into simpler molecules (and again, important to remind ourselves that this happens in an environment without oxygen) [3].

1. Hydrolysis breaks down carbohydrates, fats, and proteins into sugars, fatty acids, and amino acids.
   
2. Acidogenesis converts these into alcohols and volatile fatty acids, such as ethanol and propionic acid, with by-products of carbon dioxide, ammonia, and hydrogen sulphide.
3. Acetogenesis transforms these into hydrogen, carbon dioxide, and acetic acid.
4. Methanogenesis produces methane, water, and more carbon dioxide from the remaining hydrogen and acetic acid. 

Why is Anaerobic Digestion Important?

We don’t need to go back to Chemistry classes to realise that, by breaking down organic waste into smaller parts and from that produce energy, heat and nutrients, AD does sound like an idyllic setting that can help bridge the gap on many current challenges whilst benefitting the environment, economy, and communities.

Here’s some facts and statistics: 

1. Reduce greenhouse gas emissions by capturing methane from organic waste and displacing fossil fuels. Methane is a potent greenhouse gas that contributes to global warming. According to the International Energy Agency (IEA), biogas and biomethane could reduce global greenhouse gas emissions by 12% by 2050 [4].
2. Enhance energy reliability by producing renewable and flexible energy from domestic sources. Biogas and biomethane can provide a reliable and versatile form of energy that can complement other renewable sources, such as wind and solar. According to the IEA, biogas and biomethane could provide 20% of global gas demand by 2050 [4]. 
3. Support rural development by creating jobs and income for farmers and communities, while also creating jobs in the construction, operation, and maintenance of AD plants. According to the WBA, AD could create 10 million jobs worldwide by 2030 [5]. 
4. Improve waste management by diverting organic waste from landfill, where it would release harmful gases and leachate. Landfill is one of the main sources of methane emissions and a major environmental problem. According to the World Biogas Association (WBA), AD could treat up to 70% of the world's organic waste by 2030 [5]. 
5. Contribute to a circular economy by recovering valuable resources from waste and returning them to the soil. AD has a profound connection to the concept of circular economy, particularly through the application of digestate, the nutrient-rich by-product of the AD process. Digestate can be an invaluable asset in regenerative agriculture, a sustainable farming practice focused on restoring soil health and biodiversity.

Anaerobic Digestion and the UK Market

In the UK, AD plays a crucial role in the renewable energy strategy, supported by various policies and incentives. Companies like Bio Capital and BTS Biogas operate state-of-the-art AD plants, converting food waste and other organic materials into green energy. As of 2021, the electricity generated by Anaerobic Digestion plants had the capacity to power over 1 million homes around the UK [6].

The UK government offers various incentives, such as the Renewable Heat Incentive (RHI), Contracts for Difference (CfD), to promote the adoption and expansion of AD technology and the Smart Export Guarantee (SEG) which ensures generators are paid for the electricity they export to the grid. Additionally, grants and funding schemes are available to facilitate the development of AD plants and infrastructure, ensuring that financial barriers are minimized for both new and existing operators. 

However, there are challenges associated with AD, such as securing a steady supply of feedstock and managing the quality of digestate to meet certifications like PAS 110. These certifications assure the quality of digestate before it can be spread on fields to ensure it doesn't cause soil quality problems. 

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In conclusion, Anaerobic Digestion (AD) stands as a beacon of sustainability and innovation in waste management and renewable energy production. By transforming organic waste into valuable resources, AD not only addresses critical environmental challenges but also fosters economic growth and energy resilience.  

As we look into the future, investing in research and development, building resilient feedstock supply chains, and ensuring quality standards will unlock the full potential of anaerobic digestion. ConsensusPower invites businesses, farms, local councils and universities to join us in shaping this future. Together, we can create a cleaner, more resilient energy system that directly benefits our communities, our economy and our environment. 

[1]https://www.sciencedirect.com/topics/engineering/anaerobic-digestion#definition

[2] https://dictionary.cambridge.org/dictionary/english/feedstock

[3] ADBA (2019), The Practical Guide to AD (2nd edition). Retrieved from https://adbioresources.org

[4] https://www.iea.org/reports/outlook-for-biogas-and-biomethane-prospects-for-organic-growth

[5]World Biogas Association (WBA) | "Appropriate management of all organic wastes must be enabled NOW"

[6] https://www.biogasworld.com/news/turning-food-waste-into-energy-to-power-homes/