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Biomass for energy debated

By Dave Elliott

The use of biomass to produce electricity need not cause significant land-use tensions and Government should look to support the development of this type of power generation with Carbon Capture and Storage (CCS), according to a new policy statement by the Institution of Mechanical Engineers.

Dr Tim Fox, IMEchE’s head of energy and environment, said:
 “Our analysis shows that at the scale of current global ambitions, the cultivation of biomass for use in electricity generation need not necessarily threaten the availability of land for food production, other energy sourcing and the preservation of ecosystems.
The demand for biomass in power generation is currently very low, and even with projected future growth of this form of electricity production, the land needed to grow these crops remains relatively small compared with that required to meet future food demands.”

IMechE calculates that, globally, around 10 gigahectares of land is available, of which at present half is used for food production. By 2050, food growing might need between 4.13–8.83 Gha depending on dietary patterns. Biomass use for electricity currently supplies around 300 TWh pa globally, and might credibly rise to 3,400 TWh by 2050. It would then require around 0.22 Gha (mid range estimate), very small compared with food growing and actually smaller than the area that would be released if we switched to lower meat diets.

In the UK, biomass is used to generate about 3% of electricity at present and could expand to between 5–11%. Fox added “Using CCS technology with biomass-fired power stations also presents us with an opportunity to remove around 10% of global carbon dioxide (CO2) emissions from the atmosphere each year, effectively cleaning up emissions from other difficult to get at sources.  Biomass electricity produces low levels of carbon emissions, on a lifecycle basis, and combining it with CCS technology effectively creates so-called ‘negative emissions’ which can make a useful contribution to mitigating climate change.
Given that the exclusion of biomass from the energy mix would significantly increase the cost of reducing the CO2 emissions of the UK energy system, Government should help ensure that land-use tensions are fully understood and correctly managed.”

The IMechE sees biomass for energy as viable on a significant scale, including large wood chip burning plants. However, there have been critical views from environmental groups on the use of trees for energy, as I have reported in earlier posts. They claim that burning trees in not sustainable or carbon neutral:—worse-than-co.html. See also

There had been a critical response to this view, as I reported earlier:

However some of the environmental groups’ arguments do seem to have been supported  in a new report on Carbon Accounting of Forest Bioenergy from the European Commision’s Joint Research Centre: “The assumption of biogenic carbon neutrality is not valid under policy relevant time horizons (in particular for dedicated harvest of stemwood for bioenergy only) if carbon stock changes in the forest are not accounted for.”

It claims that the harvest of wood for bioenergy “causes a decrease of the forest carbon stock, which may not be recovered in short time, leading to a temporary increase in atmospheric CO2 and, hence, increased radiative forcing and global warming. At the local scale or stand level, the additional harvest of wood for bioenergy creates a temporary decrease of the carbon stock, compared to what would otherwise happen without harvesting. However, at the landscape or national level the mosaic of stands where forest biomass is removed for bioenergy has to be considered, and the continuous rate of wood removals could translate into a permanent decrease of carbon stock (or a lower increase compared to the reference fossil scenario)”.

It adds that “The combustion of woody biomass releases, in most cases, more CO2 in the atmosphere, per unit of delivered energy, than the fossil fuels they replace. This is because biomass normally has less energy per kg of carbon and also lower conversion efficiency. Furthermore, higher energy losses and emissions are usually incurred in collecting, transporting, processing, storing and distributing the biomass fuel compared to traditional fossil fuels. Therefore, if release of biogenic carbon is also accounted for, the bulk of the scientific literature suggests that all together these phenomena create an emission of biogenic-CO2 from forest bioenergy which is, higher than the emissions from a reference fossil system in the short term (especially in the case of bioenergy dedicated harvest of stemwood).” Basically what the FoE, the RSPB and Greenpeace said in Dirtier than Coal.

There are some small let-outs:If the forest productivity increases because of the bioenergy production, the continuous substitution of fossil fuels may, in time, recover the additional emissions of bioenergy production. In these cases, at the payback time the fossil fuel parity is reached (i.e. the bioenergy system and the fossil counterfactual have emitted the same amount of CO2 in the atmosphere). After the fossil fuel parity time, the bioenergy system starts to provide CO2 savings.” But otherwise it makes for grim reading for those keen on using wood chip to co-fire power stations, especially using imported wood!

That’s not to say that other types of biomass can’t play a role- short rotation coppice of fast growing willow or elephant grass. The absorption delay problem is less, assuming rapid replanting, and they can have higher calorific value. Forestry wastes and other residues with no other use may also yield net positive emission reductions. But burning trees, no way:

This is all about biomass for energy, not biofuels for vehicles-  the issues there are even more controversial and contested. For example Friends of the Earth have pointed  to the failure of jatropha, a biofuel crop that was long claimed could grow on “marginal land” with little inputs in Africa, i.e. not competing with food production. The reality was, FoE says, that though that it does grow on marginal land, the yields are so low that economically it’s not worth doing. Instead companies ended up growing in on high quality arable land with irrigation resulting in huge land and water grabs across Africa. See new-report-biofuel-201cwonder-crop201d-jatropha-fails-to-deliver. That doesn’t mean all bioenergy is bad. But there’s obviously a need for limits and serious regulation.

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