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Green heat infrastructure

By Dave Elliott

Imperial College has looked at Heat System Decarbonisation (PDF) in the UK in a new report. Provocatively it says solar and biomass heat can only play limited roles for direct space heating, and focuses mainly on three other low carbon system options: a shift to using hydrogen in the gas grid, the use of decarbonized electricity to run heat pumps, and the creation of local heat networks.


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Biomass – on a slow burn

The Climate Change Committee’s report on bioenergy earlier this year was somewhat more cautious than many previous studies, arguing that, at best, the UK might only get 10% of its energy from bio-source by 2050. The CCC saw bioenergy as a scare resource, with significant constraints, not least land use. This of course is a global issue, with for example, in terms liquid biofuels, there being many concerns about the environmental and social impacts of large plantations around the world. It’s not just direct land use, it’s the impacts of land use changes (‘ILUC’) that matter, which CCC say must be included, though they are hard to assess. But if at least a 50% emission reduction, below that from fossil fuels, is set as a target, there’s less room for manoeuver.

When it comes to solid biomass for heat and power production, things get a little easier in terms of land use. CCC say ‘Our core scenarios focus on the use of abandoned agricultural land’, with a range of energy crops being viable: ‘We assume in the longer term dedicated energy crop feedstocks are a mix of fast growing trees and grasses, as these crops are potentially more suitable to land of low productivity, have low lifecycle emissions and can be converted for use across the range of sectors’. But CCC see Carbon Capture and Storage as vital in many cases: ‘If CCS is not available at the scale envisaged, the amount of bioenergy required to meet the 2050 target would have to be significantly higher than 10% of primary energy demand, and would imply land use change exceeding currently estimated sustainability limits.’

They also warn that ‘given limits on domestic supply, much of the forest biomass for power and heat used in the UK will have to be imported’. Nevertheless they feel able to conclude that ‘Scenarios for global land use which take account of required food production suggest that a reasonable UK share of potential sustainable bioenergy supply could extend to around 10% (200 TWh) of primary energy demand in 2050. However, it would be unsafe at present to assume any higher levels of bioenergy supply, and even the 10% level might require some trade-offs versus other desirable environmental and social objectives (e.g.through energy crops production encroaching on land of high biodiversity value).’ But they want tighter limits: ‘the threshold for use of biomass to meet the RO should be tightened to 200 gCO2/kWh. This would represent a significant enough saving relative to gas-fired generation, allowing a margin for emissions from possible indirect deforestation.’

Clearly they do not see biomass as likely to play a major role, although they suggest that there might be range of ‘sensible smaller-scale local uses’ – such as making use of old cooking oil to run buses, using food or farm waste in anaerobic digestion plants, or using woodchip from tree surgery waste in biomass boilers. Pretty marginal then, with CCC concluding ‘The role for use of biomass in heating buildings is likely to be relatively limited in the longer term, given alternative low-carbon options such as air-source and ground-source heat pumps. Where these are not feasible, there may be opportunities for district heating using waste heat from large-scale low-carbon thermal power plants (potentially including biomass CCS) or CHP using local waste or biomass, and for biomass boilers using local biomass in rural homes.’

This may be too dismissive a view. Certainly, in practice, biomass/biogas energy options are still struggling to get going on a significant scale in the UK, with objections still emerging to some large-scale power projects, but some are still moving ahead.

E.ONs controversial 150MW biomass power station in the Royal Portbury Docks, near Bristol, has got the go ahead, despite concerns about its part reliance on imported virgin wood. It will also use dedicated energy crops, and locally sourced waste wood. E.ON has said it would set up a community investment fund, contributing £50,000 per year for charitable and educational community projects in the area, while a further £75,000 would also be set aside to trial green buses and improve cycle routes in the area.

However, E.ON told BusinessGreen that it was reviewing its plans for this and other renwable energy projects, in light of proposed changes to subsidies offered under the government’s Renewable Obligation scheme. Drax also seem to be having second thoughts again about their biomass co-firing projects, complaining that there was not enough RO support

Meanwhile, Sheffield Council is looking at plans for a £20m waste wood CHP project in the Holbrook area , following on from the agreed E.ON’s £120m 30MW waste wood biomass plant on the site of the old Blackburn Meadows power station next to the M1, now under construction. In addition, RES has plans for a 100MW biomass plant in Northumberland on Blyth River.

An energy from waste/biomass complex has also been proposed for the Ince Park development located at the Manchester Ship Canal, as a joint venture between Peel Environmental and Covanta Energy. Construction of the EfW facility is set to begin soon aiming for operation in 2015. Peel Energy has also got planning permission for a separate 20MW biomass energy facility on the site, with construction scheduled to start early next year. Plants like this, which involve combustion, are often opposed by environmentalists due to possible emissions (especially if wastes are used) and also the land-use/ biodivesity implications of large scale biomass growing/importation

In Wales, in a novel project which should avoid these issues, BiogenGreenfinch have been appointed by Gwynedd Council as the preferred bidder for the construction of a new green energy plant which will take council collected food waste and turn it into renewable energy via Anaerobic Digestion. The new AD plant, which should be running soon, will process around 11,000 tonnes of food waste each year; converting it into renewable electricity and biofertiliser for use on nearby farmland. The food waste will be collected from local homes and businesses via a collection scheme run by Gwynedd Council. The new plant will replace the existing landfill site currently situated in Llwyn Isaf and should play a major role in helping the Council meet their statutory recycling targets. It will be the second waste-fed anaerobic digestion plant built in Wales, following the construction of the Premier Foods plant last year near Newport.

In this case, the biogas is burnt to produce electricity, but AD biogas can also be added to the gas main, with, despite CCC’s rather negative assessment, the prospects for ‘green gas’ from waste AD being increasingly seen as a new possible direction for green heat supply-in Germany especially. For more:

While CCC may be a little sniffy about biogas, the new DECC/DEFRA/DfT Bioenergy Strategy is a lot more positive, as is the parallel DECC Heat Strategy. Although they do not see biogas playing a role in domestic heating directly, they do envisage biomass and biogas being used for community heating via CHP plants linked to district heating networks. I will be exploring this, and the green heating options. in my next few Blogs.

CCC report: [

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