Biomass and Sustainability
Introduction
What Is Sustainability?
There have been many approaches to sustainability over the years and many different private and public organizations have demonstrated leadership. Most recently, there have been actions to broaden the approach to sustainability and to increasingly recognize how social, economic, and environmental systems are interrelated. An example of both identifying and working to address these interconnections are the Sustainable Development Goals (SDGs). The United Nations SDGs are 17 goals with 169 targets that all 191 UN Member States have agreed to try to achieve by the year 2030.
Thus, United Nations defined the sustainable development goals as the following: (1) no poverty; (2) zero hunger; (3) good health and well-being; (4) quality education; (5) gender equality; (6) clean water and sanitation; (7) affordable and clean energy; (8) decent work and economic growth; (9) industry, innovation, and infrastructure; (10) reduced inequalities; (11) sustainable cities and communities; (12) responsible consumption and production, (13) climate action; (14) life below water; (15) life on land; (16) place, justice, and string institutions; (17) partnership for the goals (1).
How the Biomass Could Contribute to the Sustainability?
The term biomass is defined as any organic matter that is available on a renewable basis, including dedicated energy crops and trees, agricultural food and feed crop residues, aquatic plants, wood and wood residues, animal wastes, and other waste materials. The annual production of biomass is about l.7-2.0x]0H tons; however, only 6x l 09 tons are currently used for food and non-food applications. Food applications are by far most important (96.5-97%). The remainder is used in non-food applications, for example, as a feedstock for the chemical industry.
The chemical composition of biomass depends strongly on its source. Generally biomass consists of 38-50% cellulose, 23-32% hemicelluloses, and 15-25% lignin. Cellulose is a non-branched water-insoluble polysaccharide consisting of several hundred up to tens of thousands of glucose units. Cellulose is the most abundant biopolymer synthesized by nature; its amount is estimated at approximately 2xl09 tons year1. Hemicelluloses are polymeric materials although lower in molecular weight than cellulose, consisting of C6-sugars (glucose, mannose, and galactose) and C5-sugars (mainly xylose and arabinose) The third component (lignin) is a highly cross-linked polymer made from substituted phenylpropene units. It acts as glue, holding together the cellulose and hemicelluloses fibres (2).
A wide variety of biomass sources is available for further conversion and utilization. Selection of the biomass feedstock is of paramount importance from both techno- and socio-economical points of view. For ethical reasons, the biomass feedstock should not compete with the food chain. Waste streams with low or even negative value, such as agricultural waste are preferred. Furthermore, it is also advantageous to select sources that are not prone to diseases, only require a limited amount of fertilizer, have a high growth rate per hectare per year and are preferably available throughout the year.
We are entering a new age, the age of science, high technology, and science-based industry, agroforetsry, and services but we are entering the age of environmentalism as well.
BIOREFINING AS A POSSIBILITY TO OBTAIN ENERGY AND BIOPRODUCTS
The concept of biorefinery was originated in late 1990s as a result of scarcity of fossil fuels and increasing trends of use of biomass as a renewable feedstock for production of non-food products. The term of ‘Green Bioefinery’ was first introduced in 1997 as: ‘Green biorefineries represent complex (to fully integrated) systems of sustainable, environmentally and resource-friendly technologies for the comprehensive (holistic) material and energetic utilization as well as exploitation of biological raw materials in form of green and residue biomass from a targeted sustainable regional land utilization’.
According to the US Department of Energy (DOE), ‘A biorefinery is an overall concept of a processing plant where biomass feedstocks are converted and extracted into a spectrum of valuable products’. The American National Renewable Energy Laboratory (NREL) defined biorefinery as follows: ‘A biorefinery is a facility that integrates biomass conversion process and equipment to produce fuels, power and chemicals from biomass’. These definitions of biorefinery are analogous to today’s integrated petroleum refinery and petrochemicals industry to produce multitude of fuels and organic chemicals from petroleum (3).
However, we think that we have a priority because we have introduced this concept in the paper (4):
In our days, the idea that vegetable biomass represents a source of liquid fuel and of different new materials has led to the development of various research programs in this field. Our investigations in this direction are based on the following premises: (1) all kinds of vegetable biomass include almost the same components; (2) the macromolecu- lar compounds existing in the vegetable biomass incorporate biosynthesis energy, and their conversion to useful products seems to be considered; (3) the complex and total processing technology may be modulated depending on the chemical composition of the vegetable source, as well as on the utilization of the obtained chemical compounds. The possibilities of complex processing of soft- and hardwood bark, agricultural wastes, and some energetic cultures of Helianthus tuberosus and Asclepias syriaca are exemplified.
In order to face the present state of affairs, the manifested tendency is that of adopting the existing classical technologies of carbo- and petrochemical fields in processes of converting biomass into products possessing energetic and/or chemical value. The technology of integral and complex valorization of biomass has been proposed is to be performed on several stages and modules, depending on the chemical composition of the available vegetal resources and on the corresponding field of application for the obtained products as well.
A plant for the fractionation and refining of biomass and the use of its entire components is a ‘biorefinery’ plant that will have to display a high level of process integration and optimization to be competitive in the near future. Forest products companies may increase revenue by producing biofuels and chemicals in addition to wood, pulp, and paper products in a so-called Integrated Forest Biorefinery (IFBR). The concept of an IFBR is being advanced by a number of investigators who envision converting cellulose, hemicelluloses, and lignin from woody biomass, dedicated annual crops, industrial and municipal waste in bioenergy, and basic chemicals (5,6).
