Editors: Prof Dr Jo Dewulf, Prof Dr Herman van Langenhove, both of Ghent University, Belgium. Both experienced researchers in environmental chemistry and clean technology.

Renewables-Based Technology

Sustainability Assessment

John Wiley & Sons

Copyright © 2006 John Wiley & Sons, Ltd
All right reserved.
ISBN: 978-0-470-02241-2

Chapter One

The Contribution of Renewables to Society

Gran Berndes

1.1 Introduction

Stocks and flows of biomass are vital components of the biogeochemical system of the Earth. Biomass builds up the ecosystem, which contains the reservoir of genetic and species diversity and provides environmental services such as water purification, waste assimilation, soil fertility rehabilitation, water runoff regulation and flood control. Biomass is also crucial for human subsistence in other ways as it serves as food, and can be used for energy purposes and for the production of, e.g., sawn wood, paper, and various chemicals. Throughout history, human societies have ultimately depended on the management and harvest of biological (land and water) resources, and their inability to sustain their productivity have led to the end of their civilizations (Ponting, 1992).

Thus, human beings have always influenced their habitats, and still today the conversion of ecosystems to land for biomass production is perhaps the most evident alteration of the Earth. However, emissions to air and water also lead to substantial environmental impacts and a large portion of these emissions come (directly or indirectly) from other than land use activities. The industrialized society of today is unique historically in that access to biomass does not impose the ultimate limit: humans have learned to decouple industrial activities from biological productivity by exploiting fossil resources in the form of petroleum, coal and gas and this ability proved a powerful driver of societal development in the twentieth century. The role of biomass as a source of energy has steadily declined and the global energy system is today dominated by fossil fuel use. The petrochemical industry creates synthetic materials and chemicals that successfully compete with biobased products, and also the food sector has undergone dramatic changes: most of our food still comes from agriculture, but is today produced in an intensive manner that relies on fossil fuels and petroleum-based chemicals, where synthetic nitrogen fertilizers are among the crucial causes behind the past century’s transformation of world food production (Smil, 2001).

In the twentieth century, the impacts of human society on nature escalated. At the beginning of the twenty-first century, human societies have put almost half of the world’s land surface to their service, and have caused extensive land degradation and loss of biodiversity worldwide (Turner II et al., 1990, Oldeman et al., 1991, Groombridge and Jenkins, 2002). Human activities influence global biogeochemical cycles, bringing about environmental effects such as eutrophication, acidification, stratospheric ozone depletion and climate change (Figure 1.1). It is clear that the substitution of biomass with fossil resources (and the intensification of agriculture) have saved large areas from deforestation and conversion to agricultural land. But at the same time, much of the environmental impacts we see today is caused by the intensified land use and the use of petroleum, coal and fossil gas. For that reason, today there are attempts to reduce our dependence on fossil resources and return to relying more on biomass and other renewable resources for our subsistence. Addressing the concerns about climate change, land degradation and other environmental impacts, while providing food, energy and materials for a growing and wealthier global population, will be a formidable challenge.

This chapter will discuss the potential role of biomass as a renewable resource in a future global industrial society. Some analysts, such as Hoffert et al. (2002), dismiss biomass as an important future renewable resource, especially in the context of energy system transformation and climate stabilization. Others take the opposite view and propose biomass as one of the major future renewable resources (see Berndes et al., 2003 for a review of 17 studies of the global bioenergy potential). There is no way to narrowly determine the potential contribution of biomass in a future global industrial society, since it depends on a range of parameters that can vary substantially in the future (Hoogwijk et al., 2003). The aim of this chapter is instead to provide some perspectives and point out a few potentially important issues likely to come into focus in a future of extensive use of biomass for energy and as a renewable feedstock in industry. To begin with, a short review of biomass use in society, including a comparison with other major product and resource flows, followed by an outline of the prospects for non-food crop production and agricultural residue utilization in the future – emphasizing some crucial aspects that so far have received less explicit attention in assessments. After that, the drivers behind increased demand for biomass will be described. The case will be made that the demand for climate-neutral fuels and materials (especially fuels) may lead to a dramatically expanded human biomass use, with implications for biodiversity and nature conservation, and competition for land and other resources. Illustrative outlines of possible consequences are given and discussed. Finally, multifunctional biomass production systems are described. Such systems offer a way to meet the growing biomass demand while at the same time promote environmental protection and sustainable land management, thus providing a possible strategy to address concerns about climate change and also many other of the most pressing environmental problems of today.

1.2 Historic and Present Biomass Uses for Food, Energy and Materials in the World

Figure 1.2 presents a quantification of the biomass production for food, energy and materials. Other major product and resource flows are included for comparison. Figure 1.2 provides some insights in relation to the discussion of the prospects for biomass substituting for non-renewable resources in the future.

From Figure 1.2a, it is evident that the quantitative production of fossil resources is much larger than the biomass production in agriculture and forestry, implying that a far-reaching substitution of fossil resources with biomass would require a dramatic increase in the output from agriculture and forestry. Petroleum is to some extent used for the production of plastics and bulk chemicals, some 10-15% of the coal is used in steel production, and fossil gas (and to some extent also other fossil resources) are used for the production of synthetic fertilizers. But it is the use of fossil fuels in the energy sector that is the main source of society’s exploitation of fossil resources. Clearly, the decoupling of societal energy use from biological productivity, that took place more than 100 years ago, has now brought us to energy consumption levels that make it difficult to return to a situation where the global society relies solely on biomass for energy.

The situation is different when looking at materials that are presently primarily produced based on petroleum and fossil gas, e.g., plastics, rubber and various bulk chemicals (Figure 1.2b). This production presently uses 5-10% of total annual petroleum and gas production and is small compared to the agricultural output: compare, for instance, the present global production of cereals (the major crop type in agriculture) with the plastics production in the world as presented in Figure 1.2b. It is also evident from Figure 1.2b that crop production for non-food/feed uses presently occupies a very small part of agricultural land use: the major part of society’s biomass production for material purposes takes place in forestry. However, as will be shown below, agriculture can play a major future role as supplier of renewable feedstocks to industry, substituting non-renewable fossil resources, both by expanding dedicated production of non-food crops and by utilizing organic waste and residues.

The forest sector generates large amounts of biomass residues, both in the forests and at industrial sites such as sawmills and pulp/paper plants. Over the years, the forest industry has improved the wood utilization efficiency by cascading residue flows to energetic or lower value material uses. But the potential for increased residue utilization in forestry is large: increased wood extraction in connection to thinning operations and final logging may yield substantial increases in biomass output. The prospect for increased stemwood extraction by extending and/or intensifying conventional forestry operations is an issue where standpoints diverge, depending on different views regarding environmental, technical, legal and economic restrictions (Nilsson, 1996). The discussion below will focus on the agricultural sector. But several of the issues treated (e.g., the economics of biomass under an ambitious climate policy regime) are relevant also for the forest sector.

1.3 Potential Availability of Agricultural Residues and Land for Non-Food Crop Production

The total food system appropriation of biological productivity is many times larger than what is finally used by humans. Wirsenius (2003a) estimated the global appropriation of terrestrial plant biomass production by the food system to be some 13 Pg (dry matter) per year in 1992-1994. Of this, about 8% ended up in food commodities eaten. Animal food systems accounted for roughly two-thirds of the total appropriation of plant biomass, whereas their contribution to the human diet was about 13% (gross energy basis). The ruminant meat systems were found to have a far greater influence than any other subsystem on the food system’s biomass metabolism, primarily because of the lower feed-conversion efficiency of those systems. Based on this notion, one suspects that: (i) there are potentially major industrial (and energy) feedstocks to be found in the large pool of appropriated biomass not ending up as food; and (ii) there is scope for mitigating the long-term land use demand in the food sector by increases in efficiency (including dietary preferences). Both options are attractive in that they offer opportunities for increasing the use of biomass in industry, and in the energy sector, without imposing further conversion of natural land to agricultural uses.

In order to gain a better understanding of these opportunities, a mass and energy balanced model of the global food system was used to assess how the global biomass potential is influenced by different development paths in the food and agriculture system (Wirsenius, 2003a, 2003b; Wirsenius et al., 2004). The starting point for the analysis was the recent projections of global agriculture up to 2030 made by the Food and Agriculture Organization of the United Nations (FAO) (Bruinsma, 2003). In addition to the ‘Reference’ scenario, depicting the FAO projection, three explorative scenarios were developed: ‘Increased livestock productivity’ (IP); ‘Ruminant meat substitution’ (RS); and ‘More vegetarian food and less food wastage’ (VE).

The results from the scenarios indicate that if the projections made by the FAO come true, the prospects for non-food crop production will be less favourable. In the scenario depicting the FAO projection, it is estimated that total agricultural land area globally will expand from current 5.1 billion hectares to approximately 5.4 billion hectares in 2030 (Figure 1.3). This means that a major expansion of non-food crops would require even further conversion of natural to cultivated land. However, as shown in scenario IP, if livestock productivity increases faster than projected by the FAO, global land requirement for food may actually decrease to 2030. Furthermore, as shown in scenario RS and VE, if the higher livestock productivity is combined with changes in diets (a 20% substitution of ruminant meat with pig/poultry meat) and reduced food wastage, global agricultural land demand may decrease to 4.2-4.4 billion hectares (Figure 1.3). If the surplus agricultural land was targeted for non-food crop cultivation, a considerable amount of biomass could be produced without claiming land beyond what has already been appropriated.

In the IP, RS and VE scenarios, also the amount of food-system residues and by-products available for non-food purposes will be higher than in the FAO projection (Figure 1.4), mainly due to a lower use of crop residues as feed in those scenarios. In, e.g., the European regions, agricultural land demand decreases also in the Reference scenario, due to decreasing population (-8% from 1998 to 2030) and continuing rises in crop and livestock productivity. This is in contrast with the developing regions, where population growth and increasing food consumption per capita add to rising land demand, as in, e.g., Latin America.

The above scenario exercise indicates that biomass from surplus cropland and from food sector residues may indeed play a large role as a renewable feedstock and help reduce the present dependence on non-renewable energy and materials. The scope for establishment of bioenergy plantations on surplus cropland may be considerable: if the food sector development follows a path similar to that in the RS/VE scenarios, a global biomass supply from plantations of the order of 3-6 billion ton per year does not seem to be impossible with regard to the land requirements of food production. Also the potential supply of biomass residues from the food system is impressive, being of the order of 3-4 billion ton per year. However, it is also clear that food sector development – and especially dietary preferences and the development of animal production efficiency – strongly influence the potential.

It is not axiomatic that the use of biomass resources is environmentally superior to the use of non-renewable resources. Both the dedicated production of feedstock crops and the collection of residues can lead to undesired environmental impacts and it is crucial that practices are found that ensure that reduction of one environmental impact does not increase another. However, if guided in sound directions, a growing biomass demand may be instrumental in promoting sustainable land management. This will be discussed further in a later section, where it will be described how biomass plantations can be located, designed and managed so as to generate environmental benefits in addition to those associated with the substitution of nonrenewable fuels or industrial feedstocks.

1.4 Drivers Behind Increasing Demand for Biomass for Energy and Materials

There are several factors behind today’s interest in biomass as industrial feedstock and for the production of fuels and electricity. One early driver was the need to reduce food crop surpluses and find productive use of agricultural land in industrialized countries experiencing overproduction of food. Also, concern about high energy prices connected to the 1970s’ oil crisis spurred an interest in the use of domestic energy sources to reduce dependence on foreign oil. At the same time, the insight that the industrial practices and consumption patterns of the western world seriously damage the environment stimulated a search for recyclable, biodegradable and less toxic materials. In this context, biomass was seen as a potentially important domestic, renewable resource, with the potential to meet the demand for more environmentally benign feedstocks in industry as well as for the production of fuels and electricity.

However, today’s interest in biomass as a raw material for industry is not without precedents. For example, the farm chemurgy movement in the United States promoted the use of farm crops as industrial feedstocks more than half a century ago, partly due to similar concerns (Finlay, 2004). The difference is that today technology development has put us in a situation where industry can produce biofuels and bioproducts with a quality that satisfy a high consumer demand. Similar to when humans learned to use fossil feedstocks to create advanced synthetic materials with unique properties, the conversion of biomass to fuels and bioproducts continuously develops into increasingly sophisticated processes. Modern biotechnology, material science, agricultural and process engineering today allow for a number of biobased products such as biodegradable plastics, oleochemicals, biocomposites, bulk chemicals, and biofuels.

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