2019’s theme of sustainability isn’t going anywhere as we head in the next decade, and the pressure to adopt a more environmentally friendly lifestyle and even business proposition is remaining.
Last summer, in a bid to tackle toxic air pollutants, Bristol Community Transport (BCT) announced that it had opened a new permanent biomethane gas filling station, which will be used to fuel a fleet of 22 biogas-powered buses operating within the city.
The biogas used to fuel the buses is produced using a process known as anaerobic digestion (AD), which works by breaking down organic materials such as food waste and sewage. As a result, First Bus says the 22 buses, along with the additional 77 vehicles it plans to introduce in April 2020, will emit 80% less greenhouse gases and 95% less nitrogen oxides.
While the concept of using human waste to generate power may sound novel, what many people don’t know is that AD is already an important part of the renewable energy mix – and is currently powering many small businesses around the UK. For example, Opus Energy – the fifth largest energy provider for businesses – has enough AD plants in its portfolio to produce 170GWh a year (equivalent to keeping the lights on in over 54,000 houses a year).
With 72% of SMEs saying they would like energy suppliers to be more committed to renewable energy, awareness around the benefits of sustainably-sourced energy is clearly growing. With companies such as Drax Group now committing to ambitious carbon negative ambitions, businesses increasingly want to know where their energy is coming from to ensure it’s in line with their CSR policy and company brand.
So, what is AD and what makes it so great?
An introduction to anaerobic digestion
In simple terms, AD is the breakdown of organic materials into gases, with some water as a by-product.
The organic matter, which can include manure, slurry, food waste or crops, is broken down by oxygen-intolerant micro-organisms in an airtight container. This process releases biogas – a mix of methane and carbon dioxide – which can then be used as fuel, either for grid resources such as heat and electricity generation, or as biofuels for transport.
Once all the biomass has been processed, the leftover content in the tank can be dried and used as fertiliser as the high concentrate of nitrogen and potassium is great for plants.
Who can use an anaerobic digestor?
ADs have been successfully used in sewage treatment plants for many years now, as the vast quantities of wastewater and sewage processed on site provide a constant supply of organic matter. Bristol sewerage works, for example, treats around 657,000m3 of sludge and 35,000 tonnes of food waste from local homes, food manufacturers and supermarkets each year – all of which can produce as much as 34,000m3 of biomethane per day in the process.
The use of micro-scale ADs is also common within the farming industry. Due to the nature of the businesses, farm owners are much more likely to have the land required for the digestor and the materials needed to feed it, making it a perfect fit. Farmers using ADs can produce their own renewable fuel and biofertiliser, and improve waste management on site. Excess energy can also be sold back to the grid, providing them with a lucrative additional revenue stream.
Small-scale applications are becoming increasingly popular, however the amount of organic material needed to feed the digestor is currently a limiting factor.
The most important step is finding a supportive partner who can help you investigate your options – from technology viability, to arranging a power purchase agreement (PPA). Suppliers like Opus Energy will manage this process from start to finish, so do research to find out what could be best for your business.
How does AD compare in efficiency to other renewable energies?
Compared to solar and wind, one of the big advantages of AD is that it offers a constant source of energy generation. When in operation, an AD plant will run 24 hours a day, 365 days a year. In order to head towards a zero-carbon future, the UK needs a balanced mix of renewable energy technologies to ensure power stability even when the wind isn’t blowing and the sun isn’t shining.
What does the future hold for AD?
Bristol, as a case study, has demonstrated that, with a little imagination, the potential applications of AD are limitless. However, the size, expense and time required to operate an AD plant are all significant sticking points, as is the lack of awareness among many people in the mainstream. Just as city councils should be aware of its ability to support the improvement of air quality, environmentally conscious small business owners should be aware of its benefits in reducing their carbon footprint.
Beyond the water and farming industries, AD in the UK is still in its infancy, but given the UK Government’s commitment to cutting its greenhouse gas emissions and food waste, we can expect the use of AD to increase rapidly over the coming years.