Looked at holistically it could be argued that there is no such thing as a zero carbon technology, let alone a zero carbon building. Even those technologies, such as photovoltaics and wind turbines, that convert natural sources of energy into heat or electricity directly require fuel and power for manufacture, transport etc. (embedded carbon).
Biomass however suffers because there are not only carbon emissions associated with the manufacture and transportation of the hardware, but also from the processing and delivery of the fuel itself. Furthermore its definition as a renewable fuel is contingent on the carbon released during combustion being balanced against that absorbed during growth. However as these occur over different periods and in different locations the processes involved are complex. For example the plants that are used as fuel may have taken years to grow, during which time they are both absorbing and emitting CO2 from and to the immediate atmosphere. Whilst the total quantity of CO2 sequestered by the biomass during its lifetime is emitted in perhaps minutes when used as a fuel. The 2009 version of SAP takes account of the process and transport CO2 but assumes a balance between CO2 absorbed and emitted over the life of the biomass, giving emission factors for woodchip of 0.015 kgCO2/kWh and for wood pellets of 0.037, compared with 0.206 for natural gas and 0.591 for electricity.
Some consider burning biomass as a return to the ‘bad old days’ of coal fires and wood burners, with the potential for deterioration in air quality that implies. Indeed the concentration of such pollutants as NOx and fine particulates (PM10 and PM2.5) is worryingly high. A study in 2007 for the London Councils by the AEA concluded that: “...potentially increasing the contribution from small-scale wood fuelled biomass combustion to meet energy requirements in London under the London Energy Partnership scenarios may lead to a potentially substantial increase in nitrogen dioxide and particulate matter concentrations.” The study predicted that this could result in Air Quality Objectives (AQO) required of Local Authorities under the 2007 Air Quality Standards Regulations being exceeded. London
In the US a more militant stance is being taken by the Biomass Accountability Project, which is lobbying to outlaw the burning of biomass altogether. US
For the UK the problem is one of scale. The historic situation of a relatively low number of small scale installations spread out across mainly rural locations had little impact. However a recent survey by the Forestry Commission has reported an increase in the use of biomass boilers by 25% in the last two years and 86% of schools under the now truncated Building Schools for the Future programme are reported to be proposing biomass plant. Many of these new installations have been proposed to meet Local Authority requirements for a percentage of energy/carbon to be offset using on-site renewable technologies. The marginal capital cost of a biomass installation compared with other technologies can be low, hence many schemes have gone through on the basis of the economic case.
However the availability of biomass in the UK has become a major concern. Building operators procuring fuel for biomass firing have been competing with the likes of the Drax power station in North Yorkshire, which has been co-firing coal and biomass for some time. Drax was planning to increase the proportion of power generated from biomass initially to 500 MW, with new plants at Immingham, Hull and another site, yet to be announced, potentially contributing a further 900 MW. Drax. Note that industry estimates that there is a potential 5 GW of biomass generating capacity in the pipeline.
However, despite investing £80 million in co-firing in recent years and the Renewable Obligation Certificates (ROCs) awarded, in February 2010 Drax claimed that it was no longer cost effective for it to use Biomass. It complained that the low subsidy for biomass compared with wind power, along with the low cost of carbon under the Emissions Trading Scheme had forced this decision upon them. Indeed it was even considering selling 2 million tonnes of biomass it had stockpiled. Drax2
Furthermore with biomass generated electricity not benefitting from the Government’s new feed-in tariff the whole life cost of biomass is no longer looking so attractive for smaller schemes.
On the other hand the use of wood as a fuel is also being attacked, perhaps not surprisingly, by the Wood Panel Industries Federation (WPIF). Despite contrary evidence from Drax it claims that ROCs are encouraging power companies to use wood for electricity generation, since, as of June 24 2010, co-firing was eligible for 0.5 ROC and CHP could earn 2 ROCs, with the value of a ROC at that time being £49 per MWh. A study commissioned by WPIF estimated that, on average, electricity generators could pay more than double the price paid by the UK wood panel industry for its primary raw material. Woodpanel
Two reports commissioned by WPIF conclude that this is a major threat to jobs in the manufacture of wood panels, whilst the embodied carbon that would otherwise be trapped in the wood panels would be released as CO2 through combustion, potentially increasing carbon emissions by 1%, or around 6 million tonnes annually. Of course it could be argued that this carbon will eventually be released following demolition and disposal of the wood panels.
With regard to the future of biomass in the UK the Coalition Government's first Energy Statement, published in July of this year stated that it is “....taking immediate action to exploit the potential of bio-electricity and energy from waste, by grandfathering support under the Renewables Obligation (RO) for electricity from dedicated biomass, energy from waste, anaerobic digestion and advanced conversion technologies, such as pyrolysis and gasification.” A separate report on a consultation of proposals for grandfathering was published at the same time as the Energy Statement published. Grandfathering. Grandfathering is defined as “...the policy intention to maintain a fixed level of support for the full lifetime of a generating station’s eligibility for the RO (typically 20 years), from the point of accreditation.” However the support will only apply to dedicated biomass plant and not to the fuel.
In their response to the above consultation the anti-biomass lobby group Biofuelwatch expressed the view that “in the medium to longer term, we expect UK subsidies for biomass to accelerate the development of a new global trade in woodchips and wood pellets, leading to more destructive logging in many parts of the world and to more conversion of forests, grasslands and farmlands to monoculture tree plantations.” Biofuelwatch
