Anaerobic Digestion

"...Anaerobic Digestion (AD) offers many opportunities in waste recycling, not just through stabilisation of active bio-wastes and mineralisation of certain elements for added value to land, but also by offering extra income streams through the use of biogas (methane) for renewable heat and power export.

AD has been used for centuries in industrial applications, but in the large-scale applications of centralised AD (CAD), it has come into its element as has been proven for around 20 years in Germany and Scandinavia, where a wide variety of appropriate waste streams are processed and treated in this way. The importance of recycling organic matter, macro-nutrients as well as micro-nutrients is as important as reducing carbon emissions to the atmosphere for agriculture, but also the other retail and industrial links in the food chains we all depend on.

This form of biotechnology has huge potential to solve many of the interconnected issues in the development of our increasingly dominant human ecosystem. By providing a continuous flow operation, these CAD facilities can take a large throughput for a relatively small "footprint" and therefore have an attractive relative capital cost. The more recent development of fully integrated CAD facilities to take in and separate mixed, non-hazardous wastes (e.g. MSW) through Mechanical Biological Treatment (MBT) systems offers the opportunity to maximise the recycling of inert fractions of waste as well as the recycling of the biogenic resource, whilst providing heat and power for on-site use and export.

MBT systems can be designed to take a variety of locally available wastes and use an appropriate "front-end" pre-treatment system to extract the biogenic fraction (for AD), where at the end the solid fraction is a valuable compost material with more stable, balanced and homogeneous qualities that is free of pathogens and weed seeds...."