Abstract
Biomass collection could contribute to the reduction of wildfire prevention costs by obtaining solid biofuels from shrublands that pose a high fire risk, using mechanical harvesting methods that have not been sufficiently tested in shrub formations. The objective of this study is to evaluate the performance of a harvester-baler system (Biobaler WB55) for collecting rockrose (Cistus laurifolius L.) shrublands biomass, to asses the influence of the cutting rotor tool (blades or hammers) on weight and surface productivities and operating costs, as well as to determine the influence of the standing shrub biomass load on productivity and biomass collection efficiency.A 31-hour test was conducted on 21 ha of a typical Mediterranean shrubland in the centre of Spain. Data collection included time study, daily collected area, fuel consumption and bale measurements. Samples of fresh biomass from bales were collected for the determination of moisture content. The average collected biomass was 2.3 tDM·ha-1 (tonnes of dry matter per hectare), with an average productivity of 1.6 tDM·PMH-1 and an average yield of 0.7 ha·PMH-1. Better results were obtained with blades than with hammers in the cutting rotor tool (35% more collected biomass, 42% higher weight productivity, 61% higher collection efficiency and 14% greater surface productivity). The average harvest-baling costs with blades were estimated at 99.5 €∙PMH-1, 142.1 €∙ha-1 and 53.9 €∙tDM-1 (34.0 €∙tWM-1, € per tonne of wet matter), and with hammers 91.5 €∙PMH-1, 152.5 €∙ha-1 and 81.4 €∙tDM-1 (51.1 €∙tWM-1).The analysed harvester-baler was operated without difficulty in this type of vegetation and was able to collect up to 31% of the shrub biomass load in the study area. The amount of uncollected biomass and the decrease in biomass collection efficiency, as shrub biomass load increases, suggest that possible mechanical improvements are needed to improve biomass collection efficiency.
Highlights
Since the middle of the last century, fire recurrence has increased in the Iberian Peninsula and in the overall Mediterranean basin (Mayor et al 2016, Kovats et al 2014, Pausas and Fernández-Muñoz 2012)
The objective of this study was to evaluate the performance of the harvester-baler system for collecting rockrose (Cistus laurifolius L.) shrublands biomass, to asses the influence of cutting rotor tool on collection yields and operating costs, as well as to determine the influence of the standing shrub biomass load on productivity and biomass collection efficiency
According to the systematic sampling results (Table 2), the studied area was covered by rockrose (Cistus laurifolius L.) with an average height of 1.09 m and 56% crown cover
Summary
Since the middle of the last century, fire recurrence has increased in the Iberian Peninsula and in the overall Mediterranean basin (Mayor et al 2016, Kovats et al 2014, Pausas and Fernández-Muñoz 2012). According to the EU official Land Use and Cover Area Frame Survey (LUCAS 2012), six Mediterranean countries have over 50% of the EU28 shrublands (21 Mha), with half of them (10.6 Mha) located in Spain (Mediavilla et al 2017, Esteban et al 2018). In this country, more than 100,000 ha∙y-1 of wildland have burned over the last decade, with 57% being shrublands (MAPAMA 2015).
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