A series of experiments was established to characterize biochars made from four feedstocks regionally available in the Pacific Northwest (wood pellets, softwood bark, switchgrass (Panicum virgatum L.) straw, and anaerobically digested fiber) to determine their effect on five soils. Soils were amended with 9.8, 19.5, and 39.0 Mg ha−1 of each of the four biochars and evaluated for changes in pH, water holding capacity, N mineralization, and soil C. The C content of biochars derived from the herbaceous feedstocks was 60 to 67 kg kg−1 whereas that of the woody feedstocks was >75 kg kg−1. In amended soils we found that biochars, regardless of origin, significantly raised the pH of all soil types 0.1 to 0.9 units, with the greatest impact on a sand soil. The biochars increased the soil C and water holding capacity at the higher rates of amendment depending on soil and biochar type. Nitrogen mineralization rates decreased in three of the five soils across all feedstocks. There were significant correlations (r ≥ 0.9) between biochar C measured and biochar C added regardless of feedstock or soil type. Our research demonstrates that in temperate soils, biochar feedstock may not be as important a variable as soil type for increasing C content and pH but can influence N mineralization and water holding capacity.

The greenhouse gas (GHG) impact of composting a range of potential feedstocks was evaluated through a review of the existing literature with a focus on methane (CH(4)) avoidance by composting and GHG emissions during composting. The primary carbon credits associated with composting are through CH(4) avoidance when feedstocks are composted instead of landfilled (municipal solid waste and biosolids) or lagooned (animal manures). Methane generation potential is given based on total volatile solids, expected volatile solids destruction, and CH(4) generation from lab and field incubations. For example, a facility that composts an equal mixture of manure, newsprint, and food waste could conserve the equivalent of 3.1 Mg CO(2) per 1 dry Mg of feedstocks composted if feedstocks were diverted from anaerobic storage lagoons and landfills with no gas collection mechanisms. The composting process is a source of GHG emissions from the use of electricity and fossil fuels and through GHG emissions during composting. Greenhouse gas emissions during composting are highest for high-nitrogen materials with high moisture contents. These debits are minimal in comparison to avoidance credits and can be further minimized through the use of higher carbon:nitrogen feedstock mixtures and lower-moisture-content mixtures. Compost end use has the potential to generate carbon credits through avoidance and sequestration of carbon; however, these are highly project specific and need to be quantified on an individual project basis.

A n assessment of the potential impact of climate change and the concurrent increase of atmospheric carbon dioxide (CO 2 ) concentration on eastern Washington State agriculture was conducted. Climate projections from four selected general circulation models (GCM) were chosen to evaluate impacts for the periods 2010-2039, 2030-2059 and 2070-2099, identified as 2020, 2040, and 2080 scenarios, respectively. All climate projections reflect a warming future climate, but the individual GCMs vary with respect to precipitation changes -some models reflect wetter conditions and some drier. The assessment included the crops with larger economic value for the state at selected representative locations: irrigated apples at Sunnyside; irrigated potatoes at Othello; dryland wheat at Pullman (high precipitation), Saint John (intermediate precipitation), and Lind and Odessa (low precipitation). To evaluate crop performance, a cropping system simulation model (CropSyst) was utilized using historical and future climate sequences, including simulations with and without concurrent elevation of atmospheric CO 2 concentration as given by the IPCC A1B CO 2 emission projection. Crops were assumed to receive adequate water (irrigated crops) and nutrient supply and possible negative impacts from pests and diseases were not accounted for. Simulation results project that the impact of climate change on selected but economically significant crops in eastern Washington will be generally mild in the short term (i.e., next two decades), but increasingly detrimental with time (potential yield losses reaching 25% for some crops by the end of the century). However, the projected CO 2 elevation is expected to provide significant mitigation of climate change effects, and in fact result in yield gains for some crops. Yields of winter wheat, without CO 2 effect, are projected to increase 2% to 8% for the 2020 scenario, tending to decline with further warming in high precipitation locations, but continue increasing to reach a 12% gain by the 2080s in low precipitation locations. With CO 2 elevation, winter wheat yields are projected to increase by 15% for the 2020 scenario, with larger increases later in the century. Spring wheat yields are projected not to change for the 2020 scenario, and decline 10% to 15% (2040), and 20% to 26% (2080) without CO 2 effect. However, earlier planting combined with CO 2 elevation is projected to increase yields by 16% for the 2020 scenario. 191Yields of irrigated potatoes are projected to decline 9%, 15%, and 22% for the 2020, 2040, and 2080 scenarios, respectively, but these losses are significantly smaller (2 to 3%) with CO 2 elevation. Varieties with a longer duration of green leaf area, combined with elevated CO 2 , could potentially result in yield gains of 15%. However, reductions of tuber quality are a concern under warmer conditions. Apple yields are projected to decline 1%, 3%, and 4% for the 2020, 2040, and 2080 scenarios, respectively, but with projected yields increasing 6% (2020), 9% (2040), and...