In Ukraine, farmers can collect 2 to 4.5 t d.m. of straw per ha. Straw of grain crops usually has a relatively low moisture content (less than 20%) and can be granulated/baled or burned without preliminary drying. It should be noted that the best value for water content of straw is 11-15%.
The straw supply chain consists of windrowing of straw by a combine harvester, baling, collecting of bales and temporary storage near the field, loading and transportation of straw bales to a main storage facility. Based on local conditions and available machinery, some changes in this chain can be made by farmers.
Initial conditions: the duration of harvesting is 25 days, the duration of work is 10 hours/day, deductions for maintenance and repair is 5%, amortization is 10 years, the salary of the operator is 17.7 euros/day. In the following calculations, we consider three scenarios of straw harvesting: min – harvesting of 2.0 t d.m./ha; avg. – harvesting of 3.0 t d.m./ha; max – harvesting of 4.5 t d.m./ha. The large square bales are transported by a truck with a semitrailer to a storage facility at a distance of up to 10 km.
The results of the estimation of the net cost of the straw harvesting for the three volumes of biomass collection per unit area are shown in Figure below. Amortization is the main component of costs.
Cost of straw harvesting with a large square baler
The results of the feasibility study of the straw supply chain on the basis of a large square baler are given in Table below. Thus, when harvesting straw in the amount of 4.5 t d.m./ha, the simple payback period of the harvesting unit is 4.4 years. In the scenario of harvesting average biomass volumes of 3.0 t d.m., the simple payback period of such a harvesting unit is 5.8 years. At the yield of straw of 2.0 t d.m./ha, the simple payback period of the harvesting unit is 8.1 years.
Techno-economic assessment of straw harvesting
* The cost includes direct costs for harvesting biomass and deductions for equipment amortization.
** The price is equal to the sale price of straw (W15%) of 20.8 EUR/t without VAT.