Processing efficiencies in the pipeline for anaerobic digestion

anaerobic digestion system for renewable energy production

Birmingham-based biodegradable plastics firm, Aquapak, has developed a polymer that could solve the waste sorting problems faced by local authorities in the UK.

We produce 200 million tonnes of waste per year in the UK. That equates to over 8,000 tonnes per person per day. Around 45% is now recycled, but a mere 2.5% is used to generate energy so there is clearly room for improvement [1]. Waste management firms are frustrated by cultural and structural inefficiencies that prevent them from improving their profit margin and most citizens are frustrated by the amounts that still go to landfill.

Some local authorities are having to reject as much as 15% of what they find in municipal recycling containers [2]. The public are inadequately informed about what to what to put where, and many have no idea that only four of the common forms of plastic can be recycled by most treatment plants, or that synthetic textiles clog the shredding machines. Sorting through recycling is diverting council resources from awareness campaigns, and the vicious circle is doing nothing for the UK’s green credentials.

Much more waste could be used to create energy, but a debate surrounds the ideal feedstock: poultry litter and organic waste are high in moisture and likely to require drying – which may consume as much energy as it generates – unless treated by bacteria in an oxygen-free environment (anaerobic digestion). Virgin wood has a high calorific content, but ecologists prefer it to be recycled. Plastics release considerable energy but also emissions, so are best treated by pyrolysis, gasification or plasma – but these again operate at high temperatures.

So Aquapak’s development could be a game changer. It is a polymer that dissolves in water, leaving a residue that is non-toxic and recyclable, so there is no need to remove it before processing food in an anaerobic digester (of which there are more than 250 currently operating in the UK) [3]. And significantly, it has already been approved by the US Food and Drug Administration – no mean achievement, as anyone who has applied for it will know.

[1] Environmental Services Association

[2] BBC News: “Rejected recyclable waste up 84% in England since 2011, data shows

[3] WRAP Waste and Resources Action Programme UK