Biomass is currently amongst the renewable resources with the greatest potential. The use of biomass has risen significantly in recent years due to the upsurge of non-polluting energies and this growth is driving not just the enhancement of existing energy recovery technologies but also the search for new alternative sources of biomass. In this context, the regions of Galicia and North Portugal have large areas of land devoted to forests and agriculture, which generate large quantities of waste. The management of this waste, rather than producing profits, currently represents a cost for the producer. Moreover, the optimal climate conditions for wine-growing activities in both Galicia and North Portugal means that this sector has long been considered a key element of the economy of the two countries. Pruning waste, until recently considered a problem for the producer, has now become a valuable resource for the production of solid biofuels in the form of pellets, briquettes and woodchips.
Another problem is the continuous wave of wildfires that hits these regions, where lack of forest maintenance has caused the proliferation of scrublands, which along with low branches, greatly facilitates the spread of fires. The importance of this scenario has aroused great interest in society, resulting in different bodies on both sides of the border focusing their attention on improving the current situation, whilst seeking both economic and environmental benefits from existing resources.
Biomasa-AP (http://biomasa-ap.com/) was born to address this situation. This cross-border project seeks to improve the capacities of R&D centres in the regions of Galicia and North Portugal in order to optimise the exploitation and use of biomass from pruning waste, scrubland vegetation, vines and kiwis.
Biomasa-AP is co-funded by the European Regional Development Fund (ERDF) through the Interreg V-A Spain-Portugal (POCTEP) Programme 2014 – 2020, Priority Axis 1 “Intelligent growth based on cross-border cooperation to foster innovation”. The project, located in Galicia and North Portugal features the participation of 9 entities, 5 from Galicia and 4 from Portugal. The project leader is the Centro Tecnológico de Eficiencia y Sostenibilidad Energética (EnergyLab) and the project consortium is composed of: Grupo de Tecnología energética (GTE) from the University of Vigo; XERA Axencia Galega da Industria Forestal, which is participating through the Centro de Innovación y Servicios de la Madera (CIS Madeira); Fundación Empresa-Universidad Gallega (FEUGA); Instituto Enerxético de Galicia (INEGA); Instituto Politécnico de Viana do Castelo (IPVC); Instituto de Ciência e Innovação em Engenharia Mecânica e Engenharia Industrial (INEGI), Agência de Energia do Cávado (AEC) and Agência Regional de Energia e Ambiente do Alto Minho (Area Alto Minho).
The first stage of the project focused on the evaluation of the real potential of the selected high-potential unrecovered biomasses (HPUB), which, through the adaptation of specific machinery such as that acquired and tested in the project, would be available for the production of solid biofuels. This study reached the conclusion that there was over 1,000,000 ha of scrubland without trees in the Euroregion of Galicia and North Portugal (53% in Galicia and 47% in North Portugal), with a total of 500,000 ha of mechanisable land, which would represent 1.5 Mt/annum (the equivalent of 341,000 toe). There are over 100,000 ha of vineyards (20% in Galicia and 80% in North Portugal), which would represent around 38,000 ha of mechanisable land and 75,000 t/annum of green biomass, the equivalent of 17,000 toe. Around 2,500 ha (28% in Galicia and 72% in North Portugal) are devoted to the cultivation of kiwis. The vast majority of this land is mechanisable and provides 9,000 t of green biomass (1,300 toe). These figures given an idea of the enormous potential of biomass in the Autonomous Community of Galicia and northern Portugal.
The production of solid biofuels means that the biomass collected must undergo pretreatment involving a number of operations designed to achieve the quality necessary to enable it to be densified in the form of pellets or briquettes. These operations include sorting, green cleaning and screening, biomass drying (natural and/or forced) to achieve moisture contents of around 8-12%, and size reduction (shredding and grinding). Final screening may be required to achieve material of the highest quality.
The biomasses selected and collected in the project were also characterised. Based on the results, two groups of materials can be differentiated in broad terms: scrubland vegetation and conifer pruning waste from forests, and agricultural vine and kiwi pruning waste. The forest-based material has a lower ash content than the agricultural pruning waste (1.1-1.6% compared to 2.5-2.6%) and a net calorific value of just above 17 MJ/kg (above the minimum required value for the production of pellets for domestic use, >16,5 MJ/kg), while the agricultural material NCV values of less than this minimum requirement (around 15.40-16.13 MJ/kg).
High ash contents are a significant constraint in terms of producing quality solid fuels. Therefore, additives to the new biofuels were also studied, as was the removal of the finest fractions, which have a higher ash content.
Another task carried out was the development and optimisation of different technologies to avail of the energy on a small scale, such as combustion systems (experimental burner, commercial boiler and briquette stove), microgeneration (equipment based on the Organic Rankine Cycle (ORC) and gasification. All these systems were fired by the new biofuels (pellets, briquettes and woodchips), and accompanied by the relevant fluid dynamics simulations.
Different parameters were analysed in the combustion tests carried out, including combustion stability, residues formed and ash fusibility. The feasibility of the use and potential of some of these fuels as a replacement for or complement to wood (benchmark fuel) was demonstrated, although the higher quantity of ash in the composition of these fuels required good maintenance and cleaning of the burner and heat exchange systems. Satisfactory results were also obtained in both gasification and microgeneration. The use of these waste biomasses resulted in a syngas with a high calorific value (of almost 2kWh/m3), in the former case, and an efficiency in the microgeneration process of almost 96%.
Part of the success of the project revolves round the intensive dissemination and transfer work carried out from start to finish. During the course of the project, a cross-border biomass network (https://redtransfronterizabiomasa.com/) was set up to facilitate networking for different stakeholders in the sector (experts in the field, actors interested in biomass production and use, manufacturers of agricultural and forestry machinery, energy technology manufacturers, etc.). The network now has over 130 members from around 90 different organisations.
Three years after the commencement of the project, we can conclude that Galicia and North Portugal have ample biomass resources from forest pruning, vines and kiwis, in addition to scrubland vegetation, all of which can be used for energy purposes. The use of this HPUB would bring with it numerous benefits, chiefly: reduced pressure on pinewood supply (the main raw material in pellet production), mitigation of potential biomass price increases and a boost to local economies.
The recovery of this waste would also be in line with fire prevention legislation, which obliges the removal or onsite shredding of the biomass. It would also be coherent with phytosanitary recommendations on agricultural crops, which advise the removal of pruning waste in order to minimise plagues and disease.
The potential of biomass, an abundantly available resource, has thus been demonstrated, making it necessary to continue promoting the use of HPUB through the implementation of lines of grant aid to incentivise the collection, transportation and treatment of alternative biomasses and the use of equipment compatible with these fuels. This would pave the way for a new production model, i.e., the bioeconomy.