Bark is typically 10-20% of wood volume and 10-12% of weight. Bark, tops and limb volumes are fairly well documented for many countries. They form the basis for harvesting rules in forest restoration and industrial production. The recoverable quantities are reflected in the global estimates that we see for biomass.
In New Zealand I am sure that this information is available for plantations from Massey University or Scion. You’ll find that ash (including nutrients) in bark is about 3% and between 0.5% to 1% in stem wood. Highest nutrient concentrations are in the tops leaves and branches that represent annual growth. We don’t want this ash in fuel because it causes operational problems. There is abundant residue available even from forest restoration projects. Carbonization could help recover the nutrients. Forest soil scientists are excited about carbonization for forest soils. The challenge is how to economically process the residue to char. Forest residues in our area cost $40-60/dry ton delivered to a use. If you could process the residue to char in situ (without a byproduct like oil) for $50/dry ton then the cost of biochar at 33% yield would be about $150/ton C. US Forest Service has funded low temperature pyrolysis to oil with char recovery that they hope to do in the forest but oil markets and upgrading technologies are lacking. Tom From: [email protected] [mailto:[email protected]] On Behalf Of Crispin Pemberton-Pigott Sent: Sunday, December 19, 2010 6:36 AM To: 'Discussion of biomass cooking stoves'; [email protected] Cc: 'Biochar-production' Subject: Re: [Stoves] [biochar] Capturing carbon in the timber industry Thanks tom. I have not seen a % cited before for the bark. I presume that is the dry mass. Is it known on a general basis what the nutrient % is in that 20% of the dry mass? Regards Crispin ++++++++++ We have burned plantation residues in industrial boilers in New Zealand. In order to make a clean fuel the nutrient laden bark, limbs and branches are pretty well stripped and left in the soil. I think that amounts to about 20% of the total biomass. Tom
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