sustainability Article Biomass Torrefaction as a Key Driver for the Sustainable Development and Decarbonization of Energy Production Leonel J. R. Nunes 1,2,3,4,5,* and João C. O. Matias 4,5 1 IPVC—Instituto Politécnico de Viana do Castelo, Rua da Escola Industrial e Comercial de Nun’Alvares, 4900-347 Viana do Castelo, Portugal 2 proMetheus—Unidade de Investigação em Materiais, Energia e Ambiente para a Sustentabilidade, Instituto Politécnico de Viana do Castelo, Rua da Escola Industrial e Comercial de Nun’Alvares, 4900-347 Viana do Castelo, Portugal 3 ESA—Escola Superior Agrária, Refóios do Lima, 4990-706 Ponte de Lima, Portugal 4 DEGEIT—Departamento de Economia, Gestão, Engenharia Industrial e Turismo, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal; [email protected] 5 GOVCOPP—Unidade de Investigação em Governança, Competitividade e Políticas Públicas, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal * Correspondence: [email protected]; Tel.: +351-258-909-740 Received: 16 December 2019; Accepted: 25 January 2020; Published: 27 January 2020 Abstract: Climate change is a reality that affects the daily lives of people around the world, with a set of effects that are systematically felt. If there is still discussion about the real cause behind these phenomena, with differing opinions defending the anthropic origin or the origin in terrestrial cycles of geological scale, it seems to be unanimously attributed to the increased concentration of greenhouse gases—particularly to CO2. That is, whatever the source of CO2, it is commonly accepted that this is the cause of the acceleration of the climate change process, and the occurrence of extreme climate phenomena. The use of energy from renewable sources, such as solar or wind, can contribute to the replacement of energy generated from fossil sources. However, these forms of energy are dependent on uncontrollable climatic factors and are, therefore, dependent on the existence of alternatives that, when in reserve, can be activated at any time as soon as the power grid requests their activation. Thus, biomass emerges as an alternative capable of providing this answer, although it also has numerous disadvantages. Torrefaction may be the technology that corrects these drawbacks and allows for the successful use of biomass in the replacement the coal used in power generation, contributing significantly to the reduction of CO2 emissions. In addition to this possibility, it is necessary to introduce forest management models that effectively make use of all material flows generated during forestry operations, creating value-added chains, with a view toward a circular economy and resource sustainability. Keywords: forest waste management; climate change; biomass energy; torrefaction 1. Introduction Today, humankind is facing what is most likely its greatest challenge ever [1,2]. This challenge, caused by its own inability to manage a growing need for material and energy resources, has led to a state of pressure on the environment, causing imbalances in the Earth’s systems [3–5]. Of all these imbalances, the one suffering the most profound effects is the global climate system which—in addition to experiencing the simple seasonal changes that considerably affect the agricultural and forestry Sustainability 2020, 12, 922; doi:10.3390/su12030922 www.mdpi.com/journal/sustainability Sustainability 2020, 12, 922 2 of 9 forestry cycles—is also leading to frequent extreme weather phenomena, such as those being continually reported by the media worldwide [5–7]. Regardless of the ongoing discussion of the origin of the problem, with some contemporaries Sustainabilitydefending2020 the, 12 occurrence, 922 of climate change as a problem related to natural phenomena associated2 of 9 with geological scale terrestrial cycles, or with other contemporaries who attribute any and all responsibility to anthropic activity, there is little doubt that at least the acceleration of these climate cycles—ischange processes also leading stems to from frequent humankind's extreme weatherexcessive phenomena,release of gree suchnhouse as thosegases beingin its continuallyrelentless reportedpursuit by of theresources media and worldwide energy [8 [5––12]7].. RegardlessOf all the ofgreenhouse the ongoing gases, discussion the one ofthat the is originprimarily of theresponsible problem, and with released some contemporariesin the largest defendingvolume is the carbon occurrence dioxide of (CO climate2) [13, change14]. This as gas, a problem which naturally related to exists natural in the phenomena atmosphere, associated essentially with geologicalresults from scale combustion terrestrial cycles, processes, or with and other with contemporariesthe advent of the who industrial attribute revolution any and all200 responsibility years ago, to anthropicfuels traditionally activity, used there in is daily little tasks, doubt namely that at leastbiomass, the accelerationhave been replaced of these by climate fossil fuels, change which processes are stemsmuch from richer humankind’s from the energy excessive point of release view, ofenabling greenhouse the development gases in its of relentless industry and pursuit society of resources[15,16]. and energyThe aim [8–12 of]. this article is to review the processes associated with carbon dioxide emissions caused byOf the all production the greenhouse of energy gases, from thefossil one fuels, that and is which primarily renewable responsible alternatives and released can be used, in the notably largest for the substitution of coal, which is widely used for the production of electricity in coal-fired power volume is carbon dioxide (CO2)[13,14]. This gas, which naturally exists in the atmosphere, essentially resultsplants from. The combustion process of converting processes, andsolid with biomass the adventinto energy of the first industrial involves revolution collecting 200the yearsvarious ago, fuelswastes traditionally of which used it is incomposed, daily tasks, possibly namely by biomass, a process have of conversion been replaced into by product, fossil fuels, followed which by are transport to the places of consumption where the energy is used. The most common process is much richer from the energy point of view, enabling the development of industry and society [15,16]. combustion for both heat and power production through thermochemical conversion, usually in The aim of this article is to review the processes associated with carbon dioxide emissions caused cogeneration systems (Figure 1). by the production of energy from fossil fuels, and which renewable alternatives can be used, notably It is also intended to present the advantages of biomass torrefaction, which is a thermochemical for the substitution of coal, which is widely used for the production of electricity in coal-fired power conversion process that has the ability to standardize the properties of biomass, making them more plants.consistent The process with those of converting of coal. This solid article biomass also into addresses energy firstthe involvesneed to create collecting an integrated the various forest wastes of whichmanagement it is composed, model capable possibly of creating by a process a value of chain conversion that justifies into product, the use followedof forest residues by transport from to theforest places management of consumption operations, where associated the energy with is other used. supply The most chains, common particularly process those is combustionrelated to the for bothpulp heat and and paper power industry production and the through wood panels thermochemical industry, which conversion, use little usually or nothing in cogeneration of such waste systems by- (Figureproducts.1). FigureFigure 1. 1.Several Several methodologies methodologies forfor convertingconverting forest biomass into into energy energy and and byproducts, byproducts, where where forestforest waste waste must must play play a very a very important important role. role. In theIn the definition definition of biomass, of biomass, many many other other forms forms than than forest biomassforest biomass waste can waste be included, can be included, such as such agricultural as agricultural waste waste biomass biomass or even or industrialeven industrial waste. waste. 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For the discussion presented here, after the bibliographical research on the themes, the analysis of the opinions expressed by other authors