To tie-in with ou current waste campaign we take a look at anaerobic digestion in this installment of the Big Green Debate. Shaz Rahman takes a critical view of the technology whilst John Newson argues it’s one of many parts of a zero waste strategy.

No – Shaz Rahman

The idea of anaerobic digestion is a good idea in theory. Creating gas via possible waste seems to be a positive way to use what could otherwise be discarded as rubbish. On a very small scale, anaerobic digestion can work well.  The reality, however, is that we risk creating new demand for anaerobic digestion rather than tackling the problems at route source. There are better ways to deal with potential waste that could end up in anaerobic digestion.

A big problem with anaerobic digestion is the source materials that will be used in anaerobic digestion. A lot of the waste material would be better utilised elsewhere. The first priority is to reduce the amount of waste produced in the first place. A significant amount of waste that could end up in anaerobic digestion does not need to end up there. Approximately, a third of food bought ends up in bins. Many restaurants plan to throw away a percentage of the food they cook.

Rather than creating new industries to cater for our wasteful habits, we need to change those habits. If we better matched up our needs with what we use, we could better manage the smaller amount of waste produced and there would not be such a demand for waste processes, like anaerobic digestion.

The other big problem with anaerobic digestion and, in particular, large scale anaerobic digestion, is that we risk creating a large scale industry for waste that can be better dealt with elsewhere. Even if we do massively reduce the waste we create by using much less, there will still be waste that does need to be dealt with.

There are industries that claim to be environmentally friendly but have turned out not to be. One example is the biomass industry. Small scale biomass using local waste wood from farms is a good idea. However, the industry also acts in a way that is damaging to the environment. Large scale wood is being grown specifically in places like Canada and then transported across the Atlantic Ocean to be used in Britain.

The big example we have in Birmingham for a seemingly environmentally friendly waste usage system is the Tyseley incinerator. The incinerator takes Birmingham’s waste and burns it to produce electricity. On the face of it, this appears to be a good idea as electricity is being produced from waste. The problem is that the incinerator is Birmingham’s biggest carbon emitter and that it diverts waste that could be used elsewhere to use for the incinerator. Recycling rates in Birmingham are much lower than the surrounding cities because a lot of our waste is reserved for the incinerator.

The same problem could happen for anaerobic digestion. If we create a large scale industry for anaerobic digestion industry we could have source material being specifically produced for the industry.

Yes – John Newson

Digestion by bacteria is Nature’s way of dealing with food waste, in the intestines of people and animals. For centuries every town’s food waste went to pigs, chickens and cows, but it is not practical to do this on the scale of a modem city, so we should plan for digestion in Anaerobic Digestion (AD) plants, to make our wet, organic waste into useful products.

“Food waste” does not mean food fit for human consumption is being wasted, rather we are talking about all the waste from food preparation. People are wasteful with food, which needs to be tackled, but only part of food waste is avoidable, so there has to be a sustainable pathway for the remainder. My kitchen caddy has peelings, stalks, rinds, dirty paper, tea bags and floor sweepings – not the ingredients for soup!

I compost it with my garden waste, but half the households in Birmingham have no garden, so a household collection will be needed, and the waste is too contaminated for pig swill. Food is perishable – it goes off and rots. Restaurants, schools, hospitals, produce a huge volume of stuff that is not edible but is biodegradable.

Feeding waste to animals can transmit disease between species and this is the reason it was stopped. Livestock farming has a huge pollution footprint, because of the animals’ uncontrolled methane (at both ends!) – a gas 30 times more potent than CO2 as a greenhouse gas. This is the reason why FOE recommends a lower meat diet for the UK. The argument for ‘feeding’ AD plants is that the gases are enclosed, so the biogas gets burned instead of fossil gas or oil, leaving them under the ground. ‘Green gas’ from AD plants is carbon from the air, so it will be an essential part of Zero Carbon Britain.

AD’s other product is liquid fertiliser. Nutrients are returned to farms, hence AD plants in cities can reconnect our excess fertility to the fertility deficit of Britain’s soil, so we need to import less food.

There is no one answer to waste, but anaerobic digestion looks like an essential tool in the kit. AD might be abused, but that requires the right regulation, not being against the technology.