Climate change and its mitigation is rapidly becoming an item of social concern. Climate change mitigation involves reduction of atmospheric greenhouse gas concentrations through emissions reduction and or sequestration enhancement (collectively called offsets). Many have asked how agriculture and forestry can participate in mitigation efforts. Given that over 80 percent of greenhouse gas emissions arise from the energy sector, the role of agriculture and forestry depends critically on the costs of the offsets they can achieve in comparison with offset costs elsewhere in the economy. A number of researchers have examined the relative offset costs but have generally looked only at producer level costs. However there are also costs incurred when implementing, selling and conveying offset credits to a buyer. Also when commodities are involved like bioenergy feedstocks, the costs of readying these for use in implementing an offset strategy need to be reflected. This generally involves the broadly defined category of transaction costs. This dissertation examines the possible effects of transactions costs and storage costs for bioenergy commodities and how they affect the agriculture and forestry portfolio of mitigation strategies across a range of carbon dioxide equivalent prices. The model is used to simulate the effects with and without transactions and storage costs. Using an agriculture and forestry sector model called FASOMGHG, the dissertation finds that consideration of transactions and storage costs reduces the agricultural contribution total mitigation and changes the desirable portfolio of alternatives. In terms of the portfolio, transactions costs inclusion diminishes the desirability of soil sequestration and forest management while increasing the bioenergy and afforestation role. Storage costs diminish the bioenergy role and favor forest and sequestration items. The results of this study illustrate that transactions and storage costs are important considerations in policy and market design when addressing the reduction of greenhouse gas concentrations in climate change related decision making.

Materialförluster och självuppvärmning är ett vanligt problem vid lagring av biomassa i stor skala. Biomassan som lagras bryts med tiden ned av mikroorganismer och kemiska processer vilket resulterar i en förlust av torrsubstans, ofta kring 1-4% per månad. Självuppvärmningen kan leda till mycket höga temperaturer i högarna av biomassa och kan i vissa fall leda till självantändning av biomassan. I detta examensarbete utvecklas en matematisk modell bestående av 21 kopplade partiella differentialekvationer som beskriver värme- och massflöden med målet att beskriva självuppvärmning och massförlust i systemet. Med syftet att undersöka hur värme- och massflöden påverkas av högarnas geometri, storlek, kompaktering och eventuella temperaturgradienter, skapades först en modell ii COMSOL. Resultatet från dessa simuleringar används sedan för att bygga en modell i MATLAB där flödena kan undersökas tillsammans med den komplexa reaktionskinetiken. Resultatet från denna två-dimensionella modell jämförs sedan med data från pågående forskning av SLU. Resultaten visar att de simulerade värdena liknar de experimentella data från SLU men modellen har svårt att beskriva hur materialet torkar, vilket är en vanlig observation vid lagring av biomassa. Modellen visar att fukthalten i det lagrade materialet, tillsammans med andelen lättnedbrytbart material är de två viktigaste parametrar som avgör magnituden av substansförlusten och dessutom potentialen för självuppvärmning. / Loss of material and self-heating is a common problem during large-scale storage of biomass. The material is degraded by microorganisms and chemical processes which commonly result in dry matter losses of 1-4% per month. The self-heating often leads to high temperatures in the piles, which in some cases can lead to fires. In this thesis, a mathematical model consisting of 21 coupled partial differential equations describing heat and mass transfer is presented with the aim to describe the variations in heat and dry matter loss within the pile. For describing mass and heat transfer inside the biomass pile, a COMSOL model is setup, where effects of compaction, temperature gradients, shape and size of the pile are studied. Results from the COMSOL simulations are then transferred to MATLAB to simulate the complex kinetics coupled with the heat and mass transfer. The simulated results are then compared to experimental values obtained from an ongoing research project conducted by SLU. Results show that simulations do resemble experimental data but is limited in terms of describing drying process observed during storage.  Important factors highlighted are the effect of moisture content in the starting material, as well as the amount of easily degradable content in the biomass as these factors greatly determine the magnitude of both dry matter loss and heat development.

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Increasing differences in United States energy consumption and production has influenced the passing of legislation for biomass fuel production. To determine feasibility of energy crops for alternative fuels, research is needed to investigate dry matter yield over an extended harvest season; physical characteristics need to be described for potential harvesting problems; chemical characteristics described to identify selective harvest potential, optimal harvest timing, losses during harvest and storage; various harvest techniques investigated to identify potential cost savings; and impact of various storage techniques on quantity and quality of deliverable biomass. This study investigated the use of two sorghum varieties as a potential bioenergy feedstock where 20 ha were planted for three years. Standing crop samples were collected from August through January to document changes in dry matter yield, moisture, height, fiber content, proximate and ultimate analysis. The sorghum was cut and conditioned – as a two-cutting ratoon or single-cutting – using various mower-conditioners and windrow samples taken daily to determine best method of field drying, quantify dry matter loss and soil entrainment. Two storage methods were utilized – baling with wrapping in a tubeline, and chopping and compressing in bag using a modified cotton module builder – to determine best method of storage for reduced dry matter loss. The optimal time of harvest for maximum dry matter occurred with the November once-cut where 30 Mg ha^-1 was documented, but comparable yields were observed with the two-cutting scenario. Fiber content increased with maturity, peaked, and declined, while ash content and moisture decreased with maturity. The achievement of 55% moisture in January shows field curing to be necessary for transportation at any significant distance, but soil entrainment – as measured by ash concentration – was not found to be a significant problem after conditioning, multiple windrow inversions, and harvesting. The geometric mean length of particle was determined to be 1.4 to 3.7 times lower than nominal chop length, indicating potential cost savings in comminution. Dry matter loss estimates during storage proved difficult due to mobility of moisture throughout the packages, where losses were documented up to 40%. Module packages tended to have lower dry matter and constituent losses than bales.