Burning wood has worse carbon emissions than burning coal

Some thoughts about current Bio issues.

Whilst there are some good reasons to produce biogas from wood when you analyse the process on an exergy basis it is inferior to the combustion of the wood in large scale CHP as practiced in Copenhagen.

The reason the work done by the Carbon Trust signalled that AD is an effective route for biomaterials was that the work followed rules set down by the climate change committee for the analysis of biomass.

These rules were based on the assumption that the emissions from bio-based materials when burnt or converted to other forms of energy are close to zero.

This is what is termed a cradle to grate assumption.

The committees most recent report however has recommended a change in the method of analysis for biomaterials emphasising that it must be based on cradle to final use.

When this method of analysis is used then use of biomaterials in large scale CHP tops the list.

Given such plants can then be economically fitted with CCS then you get the added benefit of use of biomaterials as well as being sustainable also actually reduce CO2 emissions.

The rules of the game are changing and wise investors will be backing away from biomass boilers, understanding that their products of combustion emit more CO2 than coal and the by products of the combustion from wood may present as great or greater problems for the environment than smokeless coal. Or even some coals such as anthracite.

Coal after all is bio product processed into an excellent fuel over the millennia.

So use the wood in buildings and burn the coal gives greater CO2 savings than burning wood.

Counter intuitive certainly, but sound engineering!

William

3 Comments

  1. Sidney Clouston - March 24, 2012, 11:58 am Reply

    Dear Fellows and Friends:

    I would like to see that report, is there a website? Counter intuitive
    is right. Sustainable Forestry suggests a large percent of CO2 recovery in the new growth of renewable feedstock. I am ignorant
    of CCS haveing lost interest in methods like pumping it into oceans
    for acidic increase or finding holes to pipe it to. Costs added as
    for consideration on the bottom line. A Triple Bottom Line analysis
    is not discussed. What is the social benefit, the environment and
    profit botom line. Coal is cheap we are told, but is it? There is
    no Greenhouse Gas we hear also from some circles. Really? A
    Central Plant with Transmission and Ohm’s Law of Resistance loss
    of 5 to 10 % cost added or Distributed Generation is another level of analysis.

    I have asked for the report on wood burning added to a Coal fired power generating resource. Ground up tires were used also added
    to the coal. Just tell me how your will mitigate the emissions. Try
    planting trees? Mankind has removed 50% of the forests during the past two hundred years. Called the lungs of the Earth (Gaia)
    causes me to wonder how well anybody could function with half of their lungs removed?

  2. Louise Coke Norris - March 24, 2012, 8:46 pm Reply

    Thank you for a succinct and accurate appraisal of a worrying and ill-portrayed trend.

    Now, how to make the move from “Burn” to “Mulch”. We need to ensure that the consequences of pointless bonfires are fully understood.

    Come on gardeners, we really can make a difference!

  3. Bill Powell - March 27, 2012, 2:29 pm Reply

    Not sure what this is commenting on? Maybe 20th Feb posting concerning biomass co-firing with coal?
    YES, that’s stupid because it uses biomass in the same inefficient way we use coal in thremal power stations. YES, CHP would be better, but digging up existing streets is a coslty nightmare we don’t need. We can gasify the biomass and use existing gas mains instead. Japan has about 27,000 CHP fuel cells installed in residences by end 2011. BETTER add a heat pump to the fuel-cell CHP to reduce the energy footprint even further. That is best done at the end user, not in a thermal power station even if CHP & CCS are fitted.
    The 20th Feb item assumes that the biomass comes from standing forest that will take 35 years or more to regrow. That is a worst case, and should indeed be discouraged. But what of sugar cane waste, maize waste, etc. These are annuals. Then there is bamboo which grows about 20x faster than wood and is mature in about four years.

    Maybe this posting is about domestic boilers? If so:
    AGREE that the craze for domestic wood-burning stoves is not all that it is cracked up to be:
    – If slow burning tar builds up in the stove. Therefore best to burn fast and very hot to break-down the tar, then store the heat in a hot tank.
    – Heating have lowest energy footprint when the heat is controlled and directed to the places where most needed. Wood burning stoves have very poor ‘controlability’.

    DISAGREE that emissions from biomass are nearly as bad as from coal. See comments on 20th Feb posting.
    If converted to hydrogen in properly optimised thermo-chemical gasifier something like 90% of the biomass energy is transferred to the hydrogen. CO2 and H2 are th two final gaseous products. CCS can then be applied to the CO2 making the the process far better than carbon neutral.
    Another option is to adjust the gasifier to produce charcoal along with the ash. The result is an excellent soil conditioner containing potash and phosphorous as well as charcoal. When spread on the fields the charcoal returns carbon to the earth virtually indefinatley. There are deposits up to 6 ft deep along tha Amazon from prehistoric farmers – up to 8000 years old.
    I suspect CCS is expensive and the sequestered CO2 does no good or bad for the world. The charcoal method benefits the world in more ways than simply taking CO2 out of the atmosphere.

    CONCLUSION. Gasify biomass to hydrogen.

    Bill

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