Anaerobic digestion (AD) is rapidly becoming a vital technology to sustain towns and cities. Cities and large urban centres are where most of the world’s population live. By 2030, an estimated 59 % of the world’s population will live in urban areas, with developed countries as the most urbanized at 81 per cent. Meanwhile, in developing countries the average is projected to be around 55 per cent by 2030. Currently, the world’s cities are responsible for up to 70% of harmful greenhouse gases while occupying just 2% of its land.
AD helps to reduce the amount of urban waste (food and garden waste, sewage etc.) going to landfill – and the emissions associated with this – by recycling organic wastes to help meet power, heating and public transport needs. Meanwhile, a staggering 98% of cities in low and medium income countries do not meet World Health Organisation Standards for air quality, and in the UK, poor air quality still causes over 40,000 premature deaths every year. By also increasing air quality, AD could become a major game-changer in improving urban living.
In 2005, C40, a consortium of the world’s mega cities, was created to address climate change issues and look at ways large urban centres can reduce CO2 emissions. They have now teamed up with the World Biogas Association to publish a report on food waste, its environmental impact, and the opportunity to reduce this waste by separately collecting it and recycling it through AD.
In UK cities, AD was initially used for sewage treatment, but has now also evolved to treat food waste. Many local authorities have rolled out separate food waste collections to make better use of this resource. Others have also invested in biomethane-fuelled buses as part of their efforts to improve air quality.