• Energy Research

Abstract The energetic and environmental performance of production and distribution of the Brassica carinata biomass crop in Soria (Spain) is analysed using life cycle assessment (LCA) methodology in order to demonstrate the major potential that the crop has in southern Europe as a lignocellulosic fuel for use as a renewable energy source. The Life Cycle Impact Assessment (LCIA) including midpoint impact analysis that was performed shows that the use of fertilizers is the action with the highest impact in six of the 10 environmental categories considered, representing between 51% and 68% of the impact in these categories. The second most important impact is produced when the diesel is used in tractors and transport vehicles which represents between 48% and 77%. The contribution of the B. carinata cropping system to the global warming category is 12.7 g CO 2 eq. MJ −1 biomass produced. Assuming a preliminary estimation of the B. carinata capacity of translocated CO 2 (631 kg CO 2 ha −1 ) from below-ground biomass into the soil, the emissions are reduced by up to 5.2 g CO 2 eq. MJ −1 . The production and transport are as far as a thermoelectric plant of the B. carinata biomass used as a solid fuel consumes 0.12 MJ of primary energy per 1 MJ of biomass energy stored. In comparison with other fossil fuels such as natural gas, it reduces primary energy consumption by 33.2% and greenhouse gas emission from 33.1% to 71.2% depending on whether the capacity of translocated CO 2 is considered or not. The results of the analysis support the assertion that B. carinata crops are viable from an energy balance and environmental perspective for producing lignocellulosic solid fuel destined for the production of energy in southern Europe. Furthermore, the performance of the crop could be improved, thus increasing the energy and environmental benefits.

One of the strategies to ensure energy security and to mitigate climate change in the European Union (EU) is the establishment and the use of short rotation woody crops (SRWCs) for the production of renewable energy. SRWCs are cultivated in the EU under different management systems. Addressing the energy security problems through SRWCs requires management systems that maximize the net energy yield per unit land area. We assembled and evaluated on-farm data from within the EU, (i) to understand the relationship between the SRWC yields and spatial distribution of precipitation, as well as the relationship between SRWC yield and the planting density, and (ii) to investigate whether extensively managed SRWC systems are more energy efficient than their intensively managed counterparts. We found that SRWC yield ranged from 1.3 to 24 t ha-1 y-1 (mean 9.3±4.2 t ha-1 y-1) across sites. We looked for, but did not find a relationship between yield and annual precipitation as well as between yield and planting density. The energy inputs of extensively managed SRWC systems ranged from 3 to 8 GJ ha-1 y-1 whereas the energy ratio (i.e. energy output to energy input ratio) varied from 9 to 29. Although energy inputs (3-16 GJ ha-1y-1) were larger in most cases than those of extensively managed SRWC systems, intensively managed SRWC systems in the EU had higher energy ratios, i.e. between 15 and 62. The low energy ratio of extensively managed SRWC systems reflected their lower biomass yield per unit area. Switching from intensively managed SRWC systems to extensively managed ones thus creates an energy gap, and will require more arable land to be brought into production to compensate for the yield loss. Consequently, extensification is not the most appropriate path to the success of the wide scale deployment of SRWC for bioenergy production in the EU. © 2014 The Authors.

This study deals with approaches for a social-ecological friendly European bioeconomy based on biomass from industrial crops cultivated on marginal agricultural land. The selected crops to be investigated are: Biomass sorghum, camelina, cardoon, castor, crambe, Ethiopian mustard, giant reed, hemp, lupin, miscanthus, pennycress, poplar, reed canary grass, safflower, Siberian elm, switchgrass, tall wheatgrass, wild sugarcane, and willow. The research question focused on the overall crop growth suitability under low-input management. The study assessed: (i) How the growth suitability of industrial crops can be defined under the given natural constraints of European marginal agricultural lands; and (ii) which agricultural practices are required for marginal agricultural land low-input systems (MALLIS). For the growth-suitability analysis, available thresholds and growth requirements of the selected industrial crops were defined. The marginal agricultural land was categorized according to the agro-ecological zone (AEZ) concept in combination with the marginality constraints, so-called ‘marginal agro-ecological zones’ (M-AEZ). It was found that both large marginal agricultural areas and numerous agricultural practices are available for industrial crop cultivation on European marginal agricultural lands. These results help to further describe the suitability of industrial crops for the development of social-ecologically friendly MALLIS in Europe.

A detailed knowledge of how poplar leaf litter decomposes under Mediterranean marginal conditions can help to minimize fertilization inputs and determine the profitability and sustainability of energy crops established in these particularly sensitive areas for bioenergy. Leaf litter decomposition was monitored for 32 months using the litterbag technique in a poplar crop under short rotation conditions in a marginal Mediterranean area. In addition, nutrient dynamics, together with the production and composition of the woody and foliar biomass produced, were studied for a period of four years. Leaf litter decomposition was relatively slow, particularly during the winter months, and accelerated in early spring, coinciding with the rainy season. At the end of the decomposition study 50% of the initial litterfall was decomposed, releasing roughly 60% of the N, 40% of the K, and 70% of the P initially present in fresh leaves. Annual yields of 6.0 dry Mg ha−1 were obtained. The aerial biomass produced the first year of the second rotation cycle extracted 83, 8.7, and 29 kg ha−1 of N, P, and K, respectively, whereas the amount of nutrients that were estimated to be naturally supplied to the system through leaf litter decomposition were 180 kg ha−1 of N, 19 kg ha−1 of P, and 30 kg ha−1 of K. Therefore, four years after establishing the energy crop, leaf litter was able to release higher amounts of primary macronutrients into the environment than the nutrient uptake by the produced aboveground biomass (woody and foliar biomass).

The cultivation of bioenergy crops could be considered as sustainable; however, its use in fertile lands could conflict with food production. The general purpose of this study is to identify areas where traditional food crops are not economically sustainable, but where they could be substituted by energy crops without changing the land use in Spain. We studied the profit margin of the main crops of the country, which are wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.), the spatial location of the growing areas, and the biophysical constraints. Spain has an extended area of 9.93 million hectares, with biophysical and/or economic constraints in rainfed arable areas. Grain yields ≤1.5 Mg ha−1 are not profitable; low organic matter content is the principal biophysical constraint. The average results showed a potential of 83.33 GJ ha−1 using triticale (x Triticosecale) and 174.85 GJ ha−1 using cardoon (Cynara cardunculus L.) in arable marginal lands. The production of biomass in this area would serve to cover between 3%–5% of primary energy needs in Spain for triticale or cardoon. In this respect, establishing energy crops in marginal lands could be an instrument to enhance rural development, boost the bio-economy, and reach environmental targets.