Profitability of biomass production in relation to harvesting technology

The aim of the paper was to determine the production costs and profitability of biomass production from Virginia mallow including various harvesting technologies. The paper covered theoretical calculation of the production costs of biomass form Virginia mallow with the use of the computer application “Biocalculator”. Calculations were made for a plantation with the surface area of 5 ha and four technologies of harvesting and the product form (pressed straw, chaff). The paper determines the profitability of production of biomass from Virginia mallow for four variants of sale prices of biomass at the level of 100, 120, 140 and 150 PLN∙t-1. In case of T1 technology all assumed prices of sale of Virginia mallow biomass with the obtained production costs were profitable. On the other hand, in T3 and T4 technology, the scope of sale prices from 120 to 150 PLN∙t-1 caused that the biomass production was profitable. While, the least profitable was application of T2 technology where only at the assessment of biomass sale 150 PLN∙t-1 production was profitable and in the remaining price options the profit was not obtained.


Introduction
Biomass is one of renewable energy sources, and energy plants are a type of biomass. The term "energy plants" means annual and perennial cultivars cultivated on agricultural land and processed into biofuels, biocomponents, thermal or electric energy [1,2].
In 2010, perennial energy crops covered a symbolic surface area of ca. 10200 ha, which referred to the general area of agricultural land in the country was approximately 0.05 %.
Virginia fanpetals -Sida hermaphrodita (L.) Rusby is one of almost 200 species which belong to Sida (L.) genus mallow family (Malvaceae). However, some botanists believe that this species should be recognized as a genus due to its considerable differences in comparison to other species. While, molecular phylogenetic studies suggest a relation of Sida to Sidasodes type which occurs in South America [5.6]. Current observations and results of experiments show that in the cultivation for seeds, this perennial plant may be used for 15-20 years. Thanks to setting buds on roots in the pre-stem zone, the plant regrows every year increasing the number of stems from one in the first year to 20-30 in the fourth and following years (in the conditions of a wide distribution of plants), forming quite strongly leaved bush [7,8].
The date of harvesting stems of Virginia mallow for energy purposes is quite extensive and depends on weather conditions, condition of the soil, that influences the use of machines, biomass purpose. Harvesting takes place after a natural end of plants vegetation (October-November) or after fall ground frost. Biomass collected within this time limit has a higher water content. Stems collected in winter are less moist and include more dry mass. A winter harvesting date is sometimes necessary due to the condition of the ground. In case of harvesting of Virginia mallow on the sewage sediment or other area with a similar structure, the use of machines is possible only after its freezing. Even, with a very delayed time limit of harvesting, seeds that weakly earth up do not cause greater losses in their yields [5].
Studies carried out in IUNG-PIB indicate that the size of Virginia mallow yield is mainly influenced by the crop density. At the density of 10 thousand per hectare, regardless the soil quality, the average yield of dry mass of Virginia mallow for four years was ca. 9.5 t·ha-1 and in particular years it was from 7.9 to 11.4 t·ha-1. While, at the stock of 20 thousand per hectare, the average yield for four years on the heavy soil was 18.0 and on the light soil -16.4 t·ha-1 [9].
Virginia mallow may be harvested in one stage, which is characterised with simultaneous cutting and fragmentation with a chaff-cutter or cutting plants with harvesting with a large size press. A multi-stage harvesting may be used on a smaller area, where each stage is performed by separate machines. In the first phase, plants are cut off and in the other, fragmented or pressed when needed. The stages include respectively mowing, pressing, loading material, transport and storing [5,10].
Harvesting may be performed with rotational mowers or field straw-cutters (tractor or mobile). Field straw-cutters, in particular those with Kemper or Krone non-row unit are the most often used nowadays. These plants may be also harvested with maize harvesting combine tractors. Plants cut off with rotational, bottom-drive mowers after being formed into rolls may be collected with rolling presses or large-size pistons. Cutting units of the harvesting machines should be set at the lowest possible height of mowing to avoid losses. Some of the machines by Class and Deutz-Fahr specially adapted for cutting plants and their binding [11].
Cost effectiveness of biomass production for energy purposes depends on the size of yield and its price, area of a field and technology of harvest. Along with the increase of yield, cost per a mass unit decreases. Also, the use of modern machines with a considerable performance working on fields with big acreage enables to considerably limit the costs [12,13,22]. Selection and exploitation of the machinery park [14,15] used in the biomass production process is also important.
We may distinguish the following stages in the biomass production processes setting of a plantation, use (running) a plantation) and liquidation of a plantation. The biomass production processes are related with these stages and planning the period of plantation use should be taken into consideration in calculation of costs. The costs of setting and liquidation of a plantation referred to the years of its use will enable estimation of the average annual costs of running a plantation [16,17].
Taking into consideration profitability of biomass production we should remember about a crucial factor that includes the costs of biomass production, namely shipping of the ready good (raw material), manner of its loading and unloading (manual, mechanised). The water content of the produced biomass (from ca. 20% to even 60%), its bulk density and distance, to which it will be transported to destination (e.g. a heating plant, farm) [17,18,23].

Objective, scope, and methodology of work
The aim of the paper was to determine the production costs and profitability of biomass production from Virginia mallow including various harvesting technologies. The paper covered theoretical calculation of the production costs of biomass form Virginia mallow with the use a computer application "Biocalculator". Calculations were made for four technologies of harvesting and the product form (pressed straw, chaff). Set technologies of harvesting of Virginia mallow:  T1 -harvesting with the use of a rotational mower and small press, transport with manual loading and unloading,  T2 -harvesting with a rotational mower and rolling press, transport with bale gripper,  T3 -harvesting with a tractor chaff-cutter, continuous reception, transport with the use of two trailers (trailers use interchangeably),  T4 -harvesting with the use of a mobile field cutter, continuous reception, transport by two trailers (trailers used interchangeably). The following assumptions were accepted for calculations:  surface area of Virginia mallow cultivation: 5 ha,  yield of fresh biomass: 15 t•ha -1 ,  period of plantation use: 15 years,  amount of needed sowing material: 3 kg•ha -1 ,  dose of fertilizers in the amount of a clean component: nitrogen 35 kg•ha -1 , phosphorus 25 kg•ha -1 , potassium 40 kg•ha -1 ,  distance from a farm to a plantation: 3 km.
Costs of setting up the plantation of Virginia mallow (Kzplant) was determined as a sum of mechanization costs (Kmech), material costs (Kmat) and remaining costs (Kpoz): Mechanization costs were determined pursuant to the methodology used in the Institute of Agricultural Engineering and Computer Science of the University of Agriculture in Krakow [16,19]. They were determined as a sum of fixed costs (Kst) and variable costs (Kzm) and costs of work allocated separately (Kpr): Material costs include costs of purchase of sowing material (Ksiew), costs of purchase of mineral fertilisers (Knaw), costs of purchase of crop protection substances (Kśor) and costs of water used for spraying (Kw) and costs of a rope of pressing (Ksz).
Technical and exploitation parameters of the machinery park used for setting up the plantation of Virginia mallow and indispensable to calculate the mechanization costs were determined based on the data and standards of literature [20,21]. For calculation of exploitation costs of machines and material costs the following assumptions and prices were assumed: Costs of production of biomass from Virginia mallow was estimated with the use of computer application "Biocalculator". It was made by employees of the Department of Production Engineering and Power Industry of the University of Agriculture in Krakow as a part of the Research project no. PBZ-MNiSW -1/3/2006 titled: "Modern technologies of energy use of biomass and biodegradable waste -their conversion to energy gas fuels". One of the co-authors of the program is a thesis supervisor of this paper. The program is available at the webpage http://biob.wipie.ur.krakow.pl/biobkalk/ [24].
"Biocalculator" is an information system of complex advisory with regard to biomass production and processing as a substitute of a traditional energy carrier used for heating purposes. It has a modular character. It means that four separate modules where separated in the program which the user may use separately or in connection to the remaining ones.  Module 1: Enables estimation of the energy demand to heat a building (with traditional energy carriers or biomass) and to make an estimated energy audit of the building.  Module 2: enables estimation of the labour inputs and energy inputs for production of biomass in field crops and costs of production of biomass and energy in biomass.  Module 3: enables estimation of the labour inputs and energy inputs and costs of compact biofuels production (briquettes or pellets) from biomass.  Module 4: includes a base of technical devices for production, processing, and combustion of biomass. Module 2 was used in this paper for calculation of biomass production costs. The biomass production costs were determined as a sum of amortisation costs of a plantation (ratio of costs of setting a plantation and planned period of its use) and biomass harvesting costs in the subsequent year including four technologies of harvesting. The index of profitability of biomass production [17,18] from Virginia mallow was determined as: where: Wop -index of profitability of biomass production (-), P -value of production of biomass from Virginia mallow (PLN•year -1 ), K -costs of production of biomass from Virginia mallow (PLN•year -1 ).
Four variants of the price of biomass 100, 120, 140, 150 PLN•t -1 were used for calculations of the biomass production value. Table 1 presents an operation sheet of cultivation of Virginia mallow with suggested technological treatments to be performed in the year when the plantation was set including the analysed technologies of harvesting. Based on the calculated performance of work, labour inputs in man-hour were estimated for each treatment. These inputs in the further part of the study enable determination of labour inputs of the total labour in relation to the applied technology of harvesting. The following symbols were assumed for calculation of labour inputs:  iosnumber of persons that work on a single unit (persons),  Wt -theoretical performance (effective) of a single unit (ha·h -1 ),  W07 -exploitation performance of a single unit (ha·h -1 ),  T07operational time of a single unit (treatment duration) (h). An assumption was made in the analysis of labour inputs that Virginia mallow will be cultivated on the wasteland, thus the first treatment in the technological card was spraying and the applied chemical substance was Roundup 360L in the dose of 6 l·ha -1 . Because of the fact that in the year where plantation was set, the fight with weeds plays a key role among technological treatments. Moreover, double mechanical weeding was planned, performed by one person (14.2 man-hour) and single manual weeding performed by 3 persons (50 man-hour). The set of labour inputs and mechanization costs for setting a plantation of Virginia mallow including four applied technologies of harvesting were placed in table 2.

Research results
The biggest inputs of labour which have to be incurred on production of Virginia mallow is generated by T1 technology (harvesting with the use of a mower and small-sizes press). They are 149 man-hours which calculated per 1 ha give 29.8 man-hour per a tone of the obtained yield 2.0 man-hour. Another technology with regard to the size of labour inputs was T2 technology (harvesting with the use of a mower and rolling press). Inputs were 124.0 man-hour (24.8 man-hour•ha -1 ). When T3 technology was used for harvesting (with the use of a tractor chaff-cutter) the total labour was 118.1 man-hour which per 1 ha gives 23.6 man-hour. The highest labour inputs in this technology of harvesting were incurred for manual weeding and mowing since the treatment was performed by a single-row field chaff-cutter Z364. While the lowest labour inputs were characteristic for T4 technology (harvesting with the use of a mobile chaff-cutter) and were 92.0 man-hour (18.4 manhour•ha -1 ).  Table 3 presents a list of material expenditures which must be incurred in the year when the plantation was set up. Material consumption was determined for the area of 5 ha and to calculate material costs prices of specified material expenditures were presented. It should be said here that the assumed material inputs without including harvesting technology are identical. While, T1 and T2 technologies required the use of a rope for presses and thus differences in material costs have appeared. In T2 technology material costs were PLN 25964.3 which per 1 ha of the area gives PLN 5192.9. These costs are the highest and result mainly from application of a bigger amount of a rope than in T1. For realisation of T3 and T4 the rope is not required thus the material costs are at a similar level and are PLN 23759.5 (4751.9 PLNha -1 ). Costs of setting the plantation are a sum of mechanization costs, material costs and remaining costs such as e.g. land tax and soil analysis. To execute the objective of the paper and calculate the biomass production,  3) The paper determines profitability of biomass production from Virginia mallow for four variants of biomass sale prices 100, 120, 140 and 150 PLN•t -1 . In case of T1 technology (mowing and pressing by a small press) all set processes of sale of Virginia mallow biomass at the obtained production costs were profitable, but the highest index of profitability was characteristic for the highest price of biomass. 4) In T3 technologies (harvesting with the use of a tractor chaff-cutter) and T4 (harvesting with the use of a mobile chaff-cutter) only the scope of sale prices from 120 to 150 PLN•t -1 caused that the biomass production was profitable. While, the least profitable option was application of T2 technology (mowing, pressing with a rolling press and bale gripper where only at the price of biomass sale 150 PLN•t -1 production was profitable and in the remaining price options, profit was not obtained.