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All Biochars are Not Equal. Hugh McLaughlin, PhD, PE. Version 1 – November 13, 2009 Presented at the Northeast Biochar Symposium 2009, Amherst, MA. Director of Biocarbon Research Alterna Biocarbon Inc. hmclaughlin@alternabiocarbon.com. What is in that bag of Biochar?.
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All Biochars are Not Equal Hugh McLaughlin, PhD, PE Version 1 – November 13, 2009 Presented at the Northeast Biochar Symposium 2009, Amherst, MA Director of Biocarbon Research Alterna Biocarbon Inc. hmclaughlin@alternabiocarbon.com
What is in that bag of Biochar? • Moisture (as delivered) • Moisture is not a bad thing, but it is not worth paying for …… • Moisture is added after char production, usually to cool or passivate the char • Moisture in the bag does not mean the char will have superior moisture retention in soil – it means moisture was added …
What is in that bag of Biochar? • Moisture (as delivered) • Ash (as delivered and from what) • Converting Biomass to Char removes the moisture and much of the organic portion, but very little of the ash constituents • Ash levels are 3 to 4 x that of the dry pre-carbonization biomass • Soluble Ash is the principal pH effect of biochar addition to soils – can act like lime • Ash includes Nitrogen? – depends on test
What is in that bag of Biochar? • Moisture (as delivered) • Ash (as delivered and from what) • Mobile Matter versus Resident Matter • Mobile - can migrate out of the char • Resident - stays with the char & soil • Matter = Carbon and H&O portions • Carbon is measured for CO2 sequestration, but plants care about soluble organics and plant nutrients available in the soil
What causes the variations in Mobile and Resident Matter?What it was made from andthe way it was made.
Pyrolysis & Carbonization Reactions of Wood - above 325C = Biochar, below = Torrefied Wood
What is in that bag of Biochar? • Moisture (as delivered) • Ash Content (as delivered and from what) • Mobile Matter versus Resident Matter • Cation Exchange Capacity • ion exchange resin behavior • Adsorption Capacity • activated carbon behavior
What is in that bag of Biochar? • Moisture (as delivered) • Ash Content (as delivered and from what) • Mobile Matter versus Resident Matter • Cation Exchange Capacity • Adsorption Capacity • And why do you CARE? • - well, you did pay for it, and • it is going to be part of your garden, and • it’s effects last pretty much forever…..
What is in that bag of Biochar • and why do you CARE? • Moisture (as delivered) – You don’t care • However, Moisture Dynamics in Soil are pivotal to plant health and dictate survival • Biochar influences high moisture retention and soil aeration properties • Moisture is adsorbed by Biochar and released slowly in soil desiccation • Need soil tests to optimize biochar properties and addition levels in soils
What is in that bag of Biochar • and why do you CARE? • Moisture (as delivered) • Ash Content – short term concern • Soluble ash influences soil pH • Biochars have alkaline carbonates and hydroxides – weak and strong bases • Biochar can make pH better or worse • Biochar also has phosphorus, potassium and nitrogen in various forms – depending in the char process
What is in that bag of Biochar • and why do you CARE? • Moisture (as delivered) • Ash Content (as delivered and from what) • Mobile Matter versus Resident Matter • Mobile Matter is going to stimulate soil microbial populations • Resident Matter is the long-term biochar phenomena • Resident carbon is not the only goal
What is in that bag of Biochar • and why do you CARE? • Moisture (as delivered) • Ash Content (as delivered and from what) • Mobile Matter versus Resident Matter • Cation Exchange Capacity – pivotal in nutrient retention in soils • May be due to oxidation of resident matter or adsorption of oxygenated Dissolved Organic Matter • May develop over time in soil
What is in that bag of Biochar • and why do you CARE? • Moisture (as delivered) • Ash Content (as delivered and from what) • Mobile Matter versus Resident Matter • Cation Exchange Capacity • Adsorption Capacity - formed during char production and, hence, does not improve • Responsible for trace moisture retention in soils may prolong growing season • Responsible for adsorption/desorption of DOM, stimulates microbial populations
Pivotal Biochar properties: • Short-term Effects • Ash Content – due to pH impact • Mobile Matter – due to stimulating soil microbes, which complete for nitrogen • Long-term Effects • Resident Matter – because it contains the • Cation Exchange Capacity • Adsorption Capacity