Impacts of Biochar Use on Biofuel Sustainability
Biochar is the solid carbon-rich co-product of most thermochemical bioenergy conversion systems. When used as soil amendment in crop fields or soil restoration projects biochar has great potential value in improving the use efficiency of other inputs like fertilizer and irrigation water, and it can improve the overall greenhouse gas (GHG) balance by sequestering carbon and potentially reducing trace gas emissions from soils. As a result, the biochar co-product can make an important contribution to bioenergy system economics, both as a direct revenue stream and as a strategy for improving fuel system GHG balance to meet the requirements for Renewable Fuel Standard RIN (Renewable Identification Number) credits. However, biochar science is still in its infancy; few tools are available to predict biochar performance in different systems, and methods to account for biochar's direct and indirect effects on GHG emissions is very inconsistent in the current lifecycle assessment literature. The goal of the Biochar task is to study the effect of pine beetle-killed derived char on soil biogeochemical processes, plant growth and ecosystem GHG balance, in agricultural and forest ecosystems to facilitate the representation of these benefits in system environmental and financial performance models.
The biomass conversion process co-produces a solid residue that can be used for process-energy or as biochar, for soil enhancement applications. Thus use and efficacy of biochar plays a key role in the broader sustainability metrics of our regional feedstock system, particularly from the standpoint of the system-wide greenhouse gas (GHG) footprint as well as economic sustainability.
Characterizing biochar properties & pretreatments
It is important to characterize the biochar resulting from pyrolysis method for various reasons. It is generally accepted that variations of pyrolysis temperatures affect the basic properties of biochars produced at those temperatures. Biochar basic properties such as total porosity, porosity distribution, pH, ash content, cation exchange capacity, volatile matter content, fixed carbon content may have a significant effect on the short term and long term biochar performance in soils as well as biochar stability on the soil.
We will compare the characteristics of pine beetle killed (blue-stained) versus healthy wood chars and chars obtained from needles and branches. Biochar C,N, O,H, ash, and volatile matter concentrations will be determined using proximate and ultimate analyses. Biochar pH, cation exchange capacity and water holding capacity will be determined by conventional methods. In addition, trace metals analyses using ICP-OES will be performed to determine basic chemical composition of the biochar. Surface area and pore analyses will serve to characterize the adsorption properties of the biochar. The basic performance of the biochar may also be affected by biochar particle size.
We will generate germination data for a variety of crops as function of the different observed biochar characteristics, such as pH, particle size, pore size, cation exchange capacity, ash content and volatile matter content. Biochar performance in soils may be enhanced by inoculation techniques which aim to deposit beneficial microorganisms inside the pores of the biochar. Cool Planet has developed proprietary techniques to perform this inoculation and the inoculated biochar will be tested for performance in soils against comparable un-inoculated biochars. Laboratory potting experiments have shown enhanced yields of vegetable crops using inoculated biochars, and these results should be translate into faster reforestation efforts. Additional pretreatment methods include high temperature steam activation as well as chemical acid or base activation methods which aim to oxidize the biochar surface. These pretreatment methods are expected to create a highly porous biochar with functionalized surface which should prove effective in remediating soils contaminated with heavy metals.
Agriculture and forest field trials
Will biochar produced from beetle-killed wood be effective for: a) increase productivity in dry-land agriculture; b) increase productivity in high-value orchard crops; c) rehabilitation of critical forest soils?
To address those questions we will establish field trials (a) on corn crops in semi-arid land, at the CSU-Agricultural Research, Demonstration, and Education Center (ARDEC) under different irrigation regimes, (b) on peach orchards at the CSU Western Colorado Research Center (WCRC); and (c) in bark beetle-killed Colorado forests soils at the Fraser Experimental Forest. The biochar treatments will consist in the application of different amounts (from 15 to 30 ton/ha) of pine beetle killed wood biochar, with our without pretreatments, and alone or in combination with manure and other fertilizers. The trials will evaluate and quantify the impacts of stained-wood biochar on soil chemical, physical and biological properties and their relationship to nutrient cycling, soil water availability, plant productivity, fruit quality and greenhouse gas emissions. Overall outcome of the field trials is testing of the following schematic hypothesis.
GHG footprint studies
Methane and nitrous oxide are more powerful greenhouse gases than CO2. Production and consumption of methane and nitrous oxide from soil directly impact their global atmospheric concentrations. Biochar applications decrease soil emissions of nitrous oxide, and increase consumption of methane. However, previous research on this topic is very limited and is confined to agricultural soils and lab investigations. The impact of field applications of char on forest soils is largely unknown. We will investigate the impact of char and nitrogen fertilizer applications on emissions of carbon dioxide, nitrous oxide and methane from forest soil.
We have installed a total of four char application studies since 2009 in the Oregon Cascades, Idaho foothills, and Montana's Bitterroot Mountains. We use these sites to understand the impacts of char application following thinning treatments to improve resistance to fire, drought, pests, and disease. All locations involve evaluating char mitigation of biomass removal in comparison with retaining biomass on comparable plots. Some locations also combine char applications with fertilization designed to mitigate the impacts of removing nutrient rich biomass from nitrogen limited sites.
Benefits of char amendments focus on sequestering carbon through the long resident times of black carbon and reduced emissions of potent greenhouse gases. The existing forest sites are an ideal platform to study greenhouse gas emissions from forests amended with char because they represent an age series of char application. Based on this work it will be possible to evaluate temporal variation in char impacts on greenhouse gas emissions from forests
