Composition verification of biofuels produced from herbaceous and woody biomass using petrographic analysis.

The utilization of herbaceous biomass as a potential source of low-cost energy can benefit the environment and contribute to the economical use of renewable energy sources. Increasing the use of various types of grasses (meadow grass, hay, miscanthus, or fescue) could be a possible solution to the problem of dwindling woody biomass resources. Currently, approximately 95% of pellet production is based on material derived from cuttings and tree waste. Given the limited supply of woody biomass, pellets produced from herbaceous biomass could be essential to ensure the sustainable use of forest resources. Not only will this type of production help to reduce the environmental impact of wood harvesting and transportation, it also would increase resource efficiency. For example, grass cuttings acquired during mowing are typically composted, often leading to material decay and, consequently, the release of methane. To minimalize the emission impact of this greenhouse gas on the environment, the utilization of green waste for energy purposes seems a more desirable option. However, the production of pellets from herbaceous biomass requires different shredding and pressing techniques than woody biomass, making the process more complex. Most importantly, herbaceous pellet biomass manufacturing requires maintaining appropriate proportions of the material mix due to the differing nature of the components and, subsequently, controlling the combustion emissions they generate (especially nitrogen and chlorine). Composition control of the pellets by physico-chemical methods at the qualitative-quantitative level is often challenging. Therefore, the goal of our project was to check if such a control would be enhanced by implementing petrographic analysis. Conducted tests showed that reflected-light microscopy can be an excellent tool to distinguish between herbaceous and woody plants and to determine the component proportions of the pellets. The tests also indicated that the optimal pellet blend should contain about 40% of herbaceous and 60% (by weight) woody material, as such proportions reduce the negative environmental impacts of excessive emissions. Our results showed that combusting such samples yields from 300 to 350 mg/m³ of CO, the VOC ranged between 20 and 25 mg/m3, PM 10 and PM 2.5 contents were about 15 mg/m³, and chlorine-based chemicals (HC1) about 10 mg/m³. [ABSTRACT FROM AUTHOR]