Squandering Biomass Heat Energy Must Stop
In this article, Mark Whettall - managing director of CPV Ltd, a UK manufacturer of district heating pipe systems - questions the way in which the Renewables Obligation is encouraging conventional power stations to squander biomass – when it would be better employed in removing carbon from the country’s heating and hot water supplies.
DECC has finally announced its strategy for decarbonising heating and hot water supplies with the publishing of its report The Future of Heating: Meeting the Challenge. With this, district heating has finally gained its due recognition as a technology that can enable the efficient delivery of low-carbon heating and hot water supplies to consumers – regardless of whether they are domestic, commercial or industrial.
The key to lowering carbon is of course dependent on the energy generation technology employed and renewable sources offer the best in terms of their carbon position. Thermal technologies such as biomass boilers and biomass combined heat and power (CHP) systems are popular choices as they can easily feed energy produced into district heating networks.
The announcement by DECC has to be applauded as it really does offer a clear way to tackle a sizeable portion of the UK’s carbon emissions – particularly as around half of them come from our need for heating. Whilst the Renewable Heat Incentive (RHI) has provided much-needed support for the biomass heat sector, the Renewables Obligation (RO) has unwittingly created an incentive for the large-scale squandering of biomass fuel in conventional, coal-fired power stations. Under the RO, power producers get paid for the proportion of renewable fuel used via Renewables Obligation Certificates (ROCs) and these have a market-led monetary value for every megawatt-hour of electricity produced.
At first glance, the idea of replacing some or all of the coal burnt in these power stations with a renewable, biomass fuel would seem to be a good idea – but considering that most of them operate at an efficiency of somewhere between 20 and 30 percent, the concept takes on a whole new guise as a large proportion of the heat energy is simply allowed to vent to the atmosphere in cooling towers.
From April 2013, the UK government is starting to reduce the level of ROC support for co-firing with biomass. However, the Scottish Government has taken this a step further and recently announced that it intends on withdrawing ROC support for wood-fuelled biomass stations with an installed capacity greater than 15 megawatts - if they fail to operate as a combined heat and power plant (CHP) – i.e. utilise the heat produced in the power generation process. The Scottish approach is very welcome, but having a threshold of 15 megawatts is surely wrong – as we really should not be wasting any heat energy.
Biomass fuel must be treated as a finite resource and, as such, we must extract every milligram of carbon saving it offers. Biomass can play a much more useful role when efficiently employed in decarbonising communities via CHP systems that feed district heating networks. By producing energy locally and transporting it to each consumer via highly insulated pipes, the savings are much greater and the fuel will be targeted in a more responsible manner.
The case for this type of decentralised energy generation has never been stronger and, to do that with renewable fuels such as biomass, will deliver heating and hot water when and where it’s required. As demand grows, many of the district heating networks will be able to be interlinked as the connected loads increase – offering further economies of scale and the ability to accept additional, diverse energy sources. Although by its very nature, biomass fuel can be re-grown, there will come a tipping point when demand outstrips available supply.
With stations such as Drax in North Yorkshire having a capacity just short of four gigawatts, the amount of biomass consumed is huge and this will undoubtedly lead to adverse effects on the fuel supply chain. This waste of biomass heat energy – effectively encouraged by the Renewables Obligation – simply cannot be allowed to continue whilst the UK’s dependence on fossil fuels remains in place for heating and hot water.