Evaluation of solid biofuels made of hemp from autumn and spring harvests from two localities - Prague and Chisinau (Moldova)

Ing. Michel Kolaříková

Disertační práce

Abstract:

The main reason for use of renewable energy resources in energy sector lies in trying to replace non-renewable fossil fuels, reduce their consumption and further decrease anthropogenic emissions of greenhouse gases. Biomass is currently a significant source of energy mainly for its availability and high potential. Industrial hemp (Cannabis sativa L.) has a high yield in a short period of time and reaches a Gross calorific value similar to that of wood. Two hemp cultivars were experimentally sown in the Czech Republic and Republic of Moldova in order to determine the biomass yield from autumn and spring harvests for utilization in the form of solid fuels - briquettes. Based on inventory analysis of relevant processes, Energy balance was developed. Technological process was considered from cultivation until distribution of the final energy product. Hemp harvested as a green plant in autumn was left under a roof for losing moisture, to keep yield as high as possible and left the field for another crop in rotation system. Spring harvested biomass was left in the field till the moisture content reached 15%. Briquettes were considered to be used in small – scale boilers for heating purposes with a thermal efficiency of 80%. Autumn and spring harvests in the Republic of Moldova and in the Czech Republic, referenced as Scenarios 1,2,3,4, respectively, have produced 142.5 GJ ha-1; 102.3 GJ ha-1; 115.2 GJ ha-1 and 88 GJ ha-1 of useful heat for household heating, respectively. Energy inputs included energy of human labor, energy in fuels, in seeds, in the machines and in fertilizers with total value 16.6 GJ ha-1; 15.8 GJ ha-1; 19.3 GJ ha-1 and 18.8 GJ ha-1 in respective order for Scenarios from 1 to 4, according to common farmers in both countries. Energy return on energy invested was calculated for Scenario 1: 8.56, Scenario 2: 6.49, Scenario 3: 5.96 and Scenario 4: 4.67. From the point of view of the energy balance, the Scenario 1 - Heat from the autumn-harvested briquetted hemp in the Republic of Moldova was found as the most advantageous. Based on values from inventory analysis, Life Cycle Assessment (LCA) was developed. LCA is used to evaluate the environmental benefits on global warming, acidification and photochemical oxidation potentials of heat energy produced by briquetted hemp biomass, when compared with coal. The results show that in both impact categories, coal-based heating represents greater environmental burden. Dominant impacted categories are global warming potential (94% higher impact on environment), human toxicity potential (91%), photochemical ozone creation (89%), acidification (81%) and the fossil fuel depletion. Due to positive results of energy balance and environmental impact, we can state, that hemp appears to be a promising energy crop in humid and temperate climates and it is able to contribute solving the energy situation, especially of small scale farmers in Moldova.

Keywords

hemp, energy balance, environmental impact, solid biofuels

Jazyk práce: angličtina

Datum vytvoření / odevzdání či podání práce: 21. 9. 2017

Obhajoba závěrečné práce

• Vedoucí: doc. Ing. Jan Banout, Ph.D.
• Oponent: Petr Vaculík, externi, Jan Chyský, externi, Petr Hutla, DiS., externi

Česká zemědělská univerzita v Praze

Fakulta tropického zemědělství

Doktorský studijní program / obor:
Zemědělská specializace / Sustainable Rural Development in TS