Thursday, 10 December 2009

The Biomass Myth 2

Some more clarity on limited role of biomass in reducing the UK’s carbon emissions for the following reasons:
  •      To meet the UK’s heating demand we would have to carpet the country with biomass crops and ship more in from countries like Malaysia, Canada etc.
  •      To meet 10% of the UK’s heating demand we would have to plant energy crops on 20% of arable land in the UK, equivalent to 1 million Ha[1]
  •       Biofuels and biomass are both competing for the same resource i.e., arable land, as well as that which is required for food cultivation. The European Council has sets a binding biofuels target of 10% for road transport fuel by 2020[2]. This, if grown in the UK, will require 3 million Ha or 60% of the UK’s arable land area. If one takes into account that there are ambitious plans to scale up the use of biomass for UK power generation (15% from biomass[3]), then the area of arable land required will be much greater than available.
  •      Usually waste wood (e.g., from saw mills) is quoted as a source for biomass feedstocks, however this is not a scalable alternative; the timber for the waste wood would need to be grown somewhere (probably in Canada or Northern Europe). Trees for timber grow more slowly than energy crops do, with a yield of <5t/Ha/yr and assuming 10% is waste wood, then a net supply of only <0.5t/Ha/yr. On the other hand, energy crops (e.g. coppiced willow) provides approximately 10t/Ha/yr. Therefore the same argument regarding availability of land area would apply and waste wood biomass becomes less viable on a larger scale.
  •      Importing biomass from temperate forests such as Canada or Northern Europe is not sustainable for two reasons i.e., impact of transporting the low energy density fuel and when viewed at a worldwide scale the supply from these sources is marginal (115% of the arable land will need to be cover in bio-crops to provide for the world energy demand).
  •      It goes without saying that importing biomass (or biofuels) from tropical areas, either forests or farmed must never be considered, as it will have disastrous impact on biodiversity and land available for people to grown food, especially from the poorer South.
Biomass has a limited role in UK’s fuel mix; because of its low energy density for the area of land available, it should only be used prudently for projects that have limited alternatives for example for displacing fuel-oil in existing sites.

[1]UK Biomass Strategy suggest increasing the amount of perennial energy crops produced in the UK to to around 1 million hectares, equivalent to 17% of total UK arable land


[3] The UK Government’s Department for Energy and Climate Change (DECC) has set a target for 15% of the UK’s renewable energy to be generated by biomass by 2020.


Wolfgang F said...

Dear Prashant,

fully agree. Biomass contribution on current level of consumption is a myth! Thanks for showing that again; and thanks for showing the competing land uses. We have to be cautious.

Well, its not a zero potential. 10% might be possible. That is not nothing!

And: There are other renewables es well, you could add 15% by wind, 5 to 10% (?) by solar, some tidal generation, some geothermal ... add it up, you get some 25 to 35%.

And now? This is there efficiency comes in. We can improve efficiency by a huge amount. The passive house is real - it is not a myth. It reduces heat demand by 90%. The Loremo(.com) is real. It reduces automobile cons. by 66%. Elektronik ink is real. It reduces monitor consumption by >90%. I could go on. LED, heat recovery, ...

But: We need to use these more efficient technologies.

Nick Grant said...

Thanks Prashant

This was really useful for my report, I owe you.

We happily heat our house with wood but the rush for biomass to meet UK zero carbon building goals is very shortsighted and undermines the efficiency measures Wolfgang so rightly promotes.

Another interesting paradox is pasted below:

First biomass is not actually low carbon. Particulates, transport, NOx and other emissions aside, biomass releases large amounts of CO2. What makes it a potentially low carbon heat source is the promise to grow more wood than is consumed so as to offset the emissions in the future. An equally logical but cheaper and cleaner option would be to burn gas but offset the emissions by growing trees (these could then turned into buildings so locking up carbon and avoiding high embodied energy materials!)

However I do not seriously advocate this as a truly sustainable solution because of the limited availability of land and the problem of CO2 emitted today being absorbed over a long period of time. However this apparently non-zero carbon option would emit less carbon and other pollutants and would make considerably more sense than burning wood to heat relatively inefficient buildings.

Similar to the argument for not using the electricity from your on-site wind turbine to be zero carbon but exporting it to the grid and heating with gas. Until the grid is saturated with low carbon electrons this is a lower carbon option.

Just try explaining the paradox to a politician.


D said...

The EU27 sustainable potential has been assessed and is about 2500 TWh/year. On a pro rata basis, about 250 TWh/yr for the UK. Very useful but as Wolfgang says limited.

By the way sea freight from Montreal of a tankerload of pellets would use very little energy. I wouldn't rule it out for perhaps 3-5 percent of UK energy - given that Canada is a forest larger than Europe and with 3 inhabitants per km2.

Denmark's found that advanced district heating technology is economically viable even for Low Energy Class I (close to Passivhaus). That can use waste heat, so the emissions are lower than from biomass heat-only boilers supplying badly-insulated buildings. They're of the order of 3x less for the lower heat demand times 3x less for the lower-CO2 heat or 10x less.

Or one can do this, which is fairly near to ZC, and gas CHP in the winter.

I agree entirely with the argument for burning clean fuels sparingly and sequestering C-rich fuels; e.g. even if one doesn't want a wooden building one can turn the wood into insulation boards. When burned, 1 kWh of a H-rich fuel such as fossil methane, fossil propane or biomethane in effect only emits 50% as much CO2 as 1 kWh of C-rich fuel such as wood or straw. This takes into account the direct emissions in combustion (1.5 to 1.75x more for the solid fuel) and also the fact that a gas-burning power plant is invariably much more efficient at converting fuel into useful energy such as heat and electricity than a wood-burning appliance.

Moreover, the climate science tells us that to avoid the dreaded tipping point CO2 emissions 2000-2030 are probably much more critical than CO2 emissions in 2100. Consequently the argument for sequestering wood now and not burning it and burning gas, but less of it, is even stronger.

It would seem that this argument is unknown to politicians and beyond the thinking of many others. The significant number of people who do understand it should find a way to make the point in a more focussed way so that it does get through. All in all I think the present UK dash for biomass makes climate change worse.


Mark Tiramani said...

Hello Prashant,

Biomass->bioethanol for a Passivhaus?

As Wolfgang points out, if we reduce our houshold consumption by ~ 90% our energy horizons expand.

3 months ago we moved into our Passivhaus in Wales. Seeing is believing (or in our case monitoring energy usage is believing).

For supplementary heating on cold days we are testing a PTC on our MVHR (450-600W), and an oiled filled 1-2kW electric radiator. We are also testing a small home-made bioethanol fire of about 2kW output.

Yesterday evening the outside air temperature was 0 - 2°C.

A friend came round about 6PM and so there were 3 adults in the house instead of 2. I had to turn the heating off because the inside temperature went over 21°C in < 45 minutes.

Q. As a direct heat source for a Passivhaus such as ours: Is crop production for bioethanol not a reasonable alternative to direct primary energy usage?

Nick Grant said...

Hi Mark

I have always seen the benefit of bio ethanol stoves in passivhause being partly aesthetic. A dancing flame and some extra heat for special occasions without the need for a flue and resultant heat loss. This justifies burning Smirnoff.

As the amounts are so small it won't break the land bank but imagine running a non passivhaus school on vodka, I'd bet oil is lower carbon once agriculture and processing are taken into account.

Do love your ethanol fireplace though, great example of low tech improvisation.

Mark Tiramani said...

The image of any kind of school running on Vodka is slightly alarming ;)

Prashant Kapoor illustrates the absurdity of some of the energy targets set by governments.
The thoughts behind those targets are clouded by 200 years of fossil fuel inefficiency.

My anecdote was an attempt to illustrate how a radical shift in a building's efficiency changes the way we use, and think about, energy.
In our Passivhaus I see a bioethanol gimmick transformed into a serious heat source for an entire dwelling.

The perspective shift is > 90°. The balance starts to tip the other way.

OK, understood, bioethanol is not the best fuel for anything except a hangover.

But if we place building efficiency first it can change our behaviour and our thinking. And it may even leave room for a little indulgence.

If very high levels of energy efficiency are made the priority then the fuel source becomes secondary and targets less vague and more achievable.

Efficiency buys time and makes space for clearer thinking.

(It just occurs to me that a "house warming party" now has a whole new meaning.)

Cheap Tap said...
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