Dear Crispin, Tom, I think we need to define a minimum *carbon* content for a material to be called *biochar*. We can't call something a biochar if it has less than 1% carbon for example. So where do we draw the line? We need to include all natural biomass made into biochar like rice hulls. The material needs to have enough carbon to be useful. So I say 50% carbon a minimum to be 'excellent' biochar knowing that most all natural, clean biomass will produce a biochar with greater than 70% carbon. But open to other values to make a scale. This makes it a product with enough value for a grower to purchase and spread.
I think the product should have the carbon content defined for quality (not DAF). We should not include the oxygen and hydrogen and ash. We should calculate the percent carbon content on the biochar sample dry weight (200 deg C). If we base quality on percent fixed matter (C-H-O) after subtracting the ash I think there is a mistake. Because we 'make' more ash when we change the cations into carbonates (increasing weight) during the process. More cations from vegetative matter the more the problem. And this quantity of ash is not what we are spreading on the field. Also the carbon trapped in the ash (as CO3) is not included in the fixed carbon fraction - it should be because it comes from the organic carbon in the raw sample. These are just details and perhaps not that important. To do what I think is needed we must determine the carbon using a Leco CHN analyzer. More work with expensive equipment. But if we want to get carbon credits in the future we need to start off accurately measuring the potential CO2 we are fixing. When money is involved these details need to be addressed. Now is the time or we will be back here again at a later time. Just because the carbon content is 0.1% and the ash is 99.9% doesn't mean the product is not beneficial for an ag field. But I don't think we should call it biochar even if someone did add a spoonful into a soil mix. This rating has nothing to do with benefit to a field. That is site specific. It has something to do with label on the bag (or may in the future). Regards Frank Vegatative plant material is 10 to 20 percent. We test a lot for nutrients. It is very hard to get the customer to bring us a clean sample as it takes so very little dust and dirt to bring the ash concentration up. I think harvesting biomass for biofuel and one will not be careful to harvest clean samples. If you have 15% ash in a dry organic material. Loose 60% of the organic fraction during pyrolysis you have something like 20+ percent ash. And, as you point out, there can be biomass with much greater than 20% ash. I suggested the 50% thinking this would be high enough to include most all biomass that is made into biochar. Thinking we need some limit that if there is less than 50% carbon Frank Shields Control Laboratories, Inc. 42 Hangar Way Watsonville, CA 95076 (831) 724-5422 tel (831) 724-3188 fax [email protected] www.compostlab.com -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Crispin Pemberton-Pigott Sent: Wednesday, October 26, 2011 12:42 PM To: Discussion of biomass cooking stoves Subject: Re: [Stoves] [biochar-production] Re: Stoves Digest, Vol 14,Issue 17 Dear Frank Apart from the special case of rice hull, how could you get a 50% ash level in char? Trees are about 0.5% ash. There is not much left of the fuel if the char is 1% of the initial mass. Regards Crispin Frank, I see the ash/carbon content as a sliding scale with relative changing benefits rather than a threshold level. If biochar has less carbon than ash is there still an agronomic benefit? It is not clear how the IBI guidelines will be used. The guidelines should list those components that should be measured. The recommended levels of those components for different purposes could be separate recommendations from IBI to a certification agency. If the purpose is stability and carbon sequestration why limit counting recalcitrant carbon even if it is 0.1% carbon or, 99.9% ash? Tom _______________________________________________ Stoves mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists .org for more Biomass Cooking Stoves, News and Information see our web site: http://www.bioenergylists.org/ _______________________________________________ Stoves mailing list to Send a Message to the list, use the email address [email protected] to UNSUBSCRIBE or Change your List Settings use the web page http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org for more Biomass Cooking Stoves, News and Information see our web site: http://www.bioenergylists.org/
