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Food Waste and Anaerobic Digestion

For this week’s article, we thought we’d focus on one of the great technical feats of our time. It’s a hugely important area of sustainable innovation - a real frontier in the fight against climate change - but, confoundingly, it hasn’t always received the press attention it deserves.


The technology in question is best described as ‘controlled anaerobic digestion’. It’s being touted as a means of reducing the environmental impact of the UK’s (frankly terrifying) habit of wasting food. The UK generates 19 million tonnes of food waste each and every year. A vast chunk of this expansive waste ends up in landfills, where it breaks down into methane - which, as you likely know, accelerates global warming 23 times quicker than CO2. In the simplest possible terms, to continue to hurl food waste into our landfills at the current rate is akin to loosening our own hubcaps. 


Controlled anaerobic digestion seeks to turn a negative into a positive, converting food waste from a methane-producing nightmare into an electricity-generating asset. In layman’s terms - the only ones we can offer, unfortunately - anaerobic digestion is the process by which organic material breaks down in the absence of oxygen. Controlled anaerobic digestion is when this process occurs in a closely monitored environment, allowing for the gasses emitted to be captured and put to good use. The mechanics of this procedure are somewhat secondary in importance to the outcome: waste is allowed to break down into methane and carbon dioxide (biogas), which is then converted into usable (and green) energy after small amounts of hydrogen sulfide and other trace gases are removed. In short, decaying food produces biogas, which in turn produces energy. Not only does this avoid the burning of fossil fuels: it also actively reduces the volume of greenhouse gas being released into the atmosphere!


The potential environmental benefits of this technology are obvious, and it’s being used to combat climate change in a number of innovative ways. Given that anaerobic digestion itself is a natural process which occurs in large piles of food waste, many landfills have begun to build biogas-processing facilities which are attached to their waste-storage units. In such cases, so-called ‘landfill gas’ (methane and CO2) is funnelled from the waste facility into the biogas-processing unit, where it is converted into green energy. This process - if made more efficient, cost-effective and widespread - might allow landfills to continue to play their role in keeping our streets clean whilst attenuating the damage they do to our atmosphere.


This is, of course, an example of anaerobic digestion on an industrial scale. Bizarrely enough, it is also possible to downscale the process of harnessing biogas such that it can occur within the home. A ‘home biodigester’ allows you to transform your domestic food waste into green energy, whilst also producing a liquid fertilizer for your garden using the organic byproducts of the anaerobic digestion process. Simply fill your home biodigester with food waste from your kitchen, and it will release biogas: this, in turn, is fed into a cooking stove where it can be burnt. Next time you chef up a spaghetti bolognaise, then, remember that the leftovers can help to pay for the process of cooking your next one! It’s worth noting, however, that this technology is not yet fully developed. It’s presently considerably more effective in warm climates than cooler ones, and it’s far from readily available on the market. Nevertheless, it’s an interesting technology to watch, and may develop into a really important area of sustainable innovation in future.


Finally, controlled anaerobic digestion can also be hugely beneficial in an agricultural setting. As noted, the process of anaerobic digestion doesn’t just produce biogas: it can also be used to create a high-quality, organic fertilizer. This is particularly useful for farmers, who can use the manure from their livestock as fuel for their biodigester. A farm which produces over 100kg of manure per day will have sufficient resources to produce top-quality fertilizer ‘on tap’. This process can help to increase crop health and yield without increasing spend. More importantly, though, it allows farmers to avoid inorganic fertilizers, many of which contain ingredients which are damaging to the environment.

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