In my previous column, I said that recovering energy from plastic packaging didn’t make sense environmentally or economically. You shouldn’t take this as meaning I don’t see a role for energy from waste. Far from it, if we are to achieve a zero waste economy and meet our renewable energy targets, I believe that energy from waste (EfW) has a critical contribution to make.
What is important is deciding when energy from waste makes sense. The waste hierarchy emphasises the importance of preventing, re-using and recycling waste before recovering energy from it. However, not everything can be recycled and recovering energy from unavoidable biodegradable residual waste is preferable to landfill. This is because of the CO2 savings from the avoidance of landfill methane emissions and the potential fossil fuel substitution.
Although the Revised Waste Framework Directive now legally requires us to take account of the waste hierarchy, it is permissible to deviate from it where that would be a better environmental option. A range of environmental criteria needs to be considered, and Defra, the Welsh Government, and the Department of Environment in Northern Ireland have identified where they consider the evidence supports following the waste hierarchy or deviating from it.
Recovery from food waste and lower grade wood waste are good examples of where deviation from the hierarchy is permitted - where there is clear evidence that the option proposed is environmentally preferable to an alternative option further up the hierarchy.
I visited the Biocycle AD plant at Ludlow recently, which was one of the first food waste AD plants in the UK. It has been a great example to the UK and some 3000 people have visited it since it opened in 2006. It is a nice demonstration of a small community plant - being owned by Shropshire Council but operated by BiogenGreenfinch. It shows just how far we have come in such a short time – we have just passed the one million tonnes per year mark in terms of processing capacity. Altogether, 46 AD facilities in the UK are capable of generating 60 megawatts of renewable electricity– enough to power 40,000 homes.
It’s a great start and I’m proud of what WRAP has done to support the development of the AD industry and the food waste collections to feed it. At the same time, we are still landfilling six to seven million tonnes of food waste each year and there is still much more to do. Even after improved waste prevention has had an impact, we will need a lot more food waste capacity. WRAP will continue to work to demonstrate the viability of AD and build investor confidence. We launched the £10 million AD loan fund last year and we were pleased to announce the first loan to Malaby Biogas in January. The second round of the fund is open until April.
AD is also a good way of recycling nutrients: if the plant is operated to PAS110, the digestate can be used as a bio-fertiliser to help grow crops. This cuts the use of inorganic fertilisers and mined nutrients such as phosphate and potash, and adds organic matter back to soil. We expect this important market to grow, particularly as the price of inorganic fertilisers rises and global pressure on food continues in the coming years. Developing markets for quality digestate is also an important part of building confidence. We are running a set of field experiments across Great Britain to show how digestate can be used as a biofertiliser, whilst maintaining crop quality and yields. We will be publishing the first year’s results later this spring, but early indications are positive, in-line with anecdotal evidence from farmers and growers.
Wood waste is a priority waste stream for all governments in the UK. Both the Scottish and English governments are considering restrictions on landfilling wood. There are good recycling markets for higher grade waste wood - in applications including panel board, landscaping and animal bedding. We are trying to help the wood recycling industry agree a quality protocol with the Environment Agency for these applications which would expand these markets. Lower grade wood, contaminated with preservative treatments will remain difficult to recycle though and I believe energy from waste has an important role to play here.
Our recent Wood Market Situation Report suggested that as much as 1.7 million tonnes per year of such wood could be going to landfill. Wood is such a good renewable fuel that this really is a waste. Furthermore, the Wood Recycling Association reports that countries with better-developed infrastructures for energy recovery took half a million tonnes of waste wood from the UK in 2010, a six-fold increase on 2009 exports. While this is a positive development in terms of reducing waste to landfill, if we had the infrastructure, this wood waste could be helping the UK reach its renewable energy targets.
Waste wood tends to be geographically dispersed creating almost a diseconomy of scale and lending itself to smaller plants. Creating a network of collection hubs would be one way to deal with this and we are looking into that. At the same time, a system based on small local plant could offer a great opportunity to develop high efficiency CHP plants feeding local heat networks. It is an area where advanced thermal technologies like gasification and pyrolysis could come into their own. It is a great idea, but with many hurdles to overcome - we shouldn’t underestimate the difficulty of making these technologies work on a commercial scale. There is also the Waste Incineration Directive (WID) to comply with which is relatively expensive – especially for smaller plants.
I have always been quite sceptical of the feasibility of using these technologies for waste – earlier in my career I worked on coal gasification and getting that to produce a gas clean enough for power generation is difficult enough. However, I visited one of Ogen UK’s plants last week and was surprised to see how much progress was being made. They have managed what I have always considered as the holy grail, a small scale WID compliant waste wood gasification plant producing gas clean enough to burn in a gas engine. The plant I saw was designed to gasify around 30,000 tonnes per year of wood and generate some 4 megawatts of renewable electricity. It was also installing a hot water feed to a local retail park to provide renewable heat.
Recovering energy from food and wood waste are priorities, but as I say above, energy recovery from unavoidable biodegradable residual waste is also preferable to landfill. Solid recovered fuel (SRF) and refuse derived fuel (RDF) present opportunities to exploit the embedded energy within residual waste. Both are already being produced to a range of different specifications that can be baled, transported and used where needed. There are still around 35 - 40 million tonnes of residual waste not recycled or recovered from the UK’s municipal, commercial and industrial waste streams. However, some 40% of this is food, green waste, paper or card and as more is recovered and recycled through other routes, the suitability of residual waste for EfW may diminish. We also estimate that over 25% of current residual waste is non-combustible.
WRAP estimates that using waste wood, residual waste, green waste and food waste for energy could meet about 2% of the UK’s total energy demand in 2020 and make a 14% contribution to the UK’s renewable energy target. It would have to be used as heat or as a transport fuel to do this though. If it was used at lower efficiency for straight power generation, the contribution would be much lower, only meeting around 4% of the target. Thus energy from waste can make an important contribution to UK energy supply but it will not transform the UK’s security of supply – it is not a ‘silver bullet’. It is however, an essential component of delivering a zero waste economy.
- To help local authorities and businesses use the waste hierarchy more effectively, WRAP has produced guidance tool at www.wrap.org.uk/business.
- The wood market situation report is available on the WRAP website: www.wrap.org.uk/msr
- Businesses looking to recover energy on a small scale from non-recyclable should contact the EfW team at firstname.lastname@example.org
Marcus Gover is Director of the Closed Loop Economy at WRAP