Energy Crops and Methane: Process Optimization of Ca(OH)2 Assisted Thermal Pretreatment and Modeling of Methane Production.

Switchgrass earned its place globally as a significant energy crop by possessing essential properties such as being able to control erosion, low cost of production, biomass richness, and appeal for biofuel production. In this study, the impact of a Ca(OH)2-assisted thermal pretreatment process on the switchgrass variety Shawnee for methane fuel production was investigated. The Ca(OH)2-assisted thermal pretreatment process was optimized to enhance the methane production potential of switchgrass. Solid loading (3-7%), Ca(OH)2 concentration (0-2%), reaction temperature (50-100 °C), and reaction time (6-16 h) were selected as independent variables for the optimization. Methane production was obtained as 248.7 mL CH4 gVS-1 under the optimized pretreatment conditions. Specifically, a reaction temperature of 100 °C, a reaction time of 6 h, 0% Ca(OH)2, and 3% solid loading. Compared to raw switchgrass, methane production was enhanced by 14.5%. Additionally, the changes in surface properties and bond structure, along with the kinetic parameters from first order, cone, reaction curve, and modified Gompertz modeling revealed the importance of optimization.

Composting of spent mushroom compost, carnation wastes, chicken and cattle manures.

This study has purposed to determine the optimum mixture ratio of used mushroom compost, chicken manure, cattle manure and carnation waste for composting. For this purpose, these materials have been mixed in seven various ratios (R1-R7) and composted in the experimental composting reactors. The highest dry material losses and temperature values have been obtained by the R4 which contains 50% carnation waste, 25% chicken manure and 25% spent mushroom compost. Beside R4, mixtures of R2, R5 and R6 have also provided high process temperature and dry material loss values. The lowest dry material loss and temperature values have been obtained in the R7 which contains only carnation wastes. In the study, it has also seen that FAS (free air space) parameter is effective on the process and must be in the interval of 24-32%.

Effects of air flow directions on composting process temperature profile.

In this study, chicken manure mixed with carnation wastes was composted by using three different air flow directions: R1-sucking (downward), R2-blowing (upward) and R3-mixed. The aim was to find out the most appropriate air flow direction type for composting to provide more homogenous temperature distribution in the reactors. The efficiency of each aeration method was evaluated by monitoring the evolution of parameters such as temperature, moisture content, CO(2) and O(2) ratio in the material and dry material losses. Aeration of the reactors was managed by radial fans. The results showed that R3 resulted in a more homogenous temperature distribution and high dry material loss throughout the composting process. The most heterogeneous temperature distribution and the lowest dry material loss were obtained in R2.

Composting of goat manure and wheat straw using pine cones as a bulking agent.

This study aimed to determine the optimum mixture ratio of pine cones, goat manure and wheat straw and obtained optimal Free Air Space (FAS) values for composting. For this aim, pine cones were added at different ratios into goat manure and wheat straw mixtures. So, the FAS value of mixtures was fixed at four different levels. According to the results, the highest organic matter degradation and temperature value were obtained at the mixture ratio of 10% pine cones, 45% goat manure and 45% wheat straw. FAS value of this mixture was 32.8.

Composting dynamics and optimum mixture ratio of chicken manure and vineyard wastes.

Vineyard waste and chicken manure mixtures are useful materials for composting but when these wastes are composted alone, many environmental problems occur because of their chemical characteristics. Whereas chicken manure is a very rich source of nitrogen, vineyard waste has a very high carbon content. In the present study experiments to determine an optimum mixture ratio of chicken manure and vineyard waste for composting were performed. The results showed that the optimum mixture ratio for composting these materials was 50% chicken manure and 50% vineyard waste on a dry basis.