IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group III: Mitigation of Climate Change Synthesizing the potentials from Chapters 4 to 10 involving biomass

Biomass supplies originate in agriculture (residues and cropping), forestry, waste supplies, and in biomass processing industries (such as the paper & pulp and sugar industries). Key applications for biomass are conversion to heat, power, transportation fuels and biomaterials. Information about biomass supplies and utilization is distributed over the relevant chapters in this report and no complete integrated studies are available for biomass supply-demand balances and biomass potential.

Biomass demand from different sectors

Demand for biomass as transportation fuel involves the production of biofuels from agricultural crops such as sugar cane, rape seed, corn, etc., as well as potentially ‘second-generation’ biofuels produced from lignocellulosic biomass. The first category dominates in the shorter term. The penetration of second-generation biofuels depends on the speed of technological development and the market penetration of gasification technology for synfuels and hydrolysis technology for the production of ethanol from woody biomass. Demand projections for primary biomass in Chapter 5 are largely based on WEO-IEA (2006) global projections, with a relatively wide range of about 14 to 40 EJ of primary biomass, or 8–25 EJ of fuel. However, there are also higher estimates ranging from 45 to 85 EJ demand for primary biomass in 2030 (or roughly 30–50 EJ of fuel) (see Chapter 5).

Demand for biomass for power and heat is considered in Chapter 4 (energy). Demand for biomass for heat and power will be strongly influenced by the availability and introduction of competing technologies such as CCS, nuclear power, wind energy, solar heating, etc. The projected demand in 2030 for biomass would be around 28–43 EJ according to the data used in Section These estimates focus on electricity generation. Heat is not explicitly modelled or estimated in the WEO, resulting in an under-estimate of total demand for biomass.

Industry is an important user of biomass for energy, most notably the paper & pulp industry and the sugar industry, which both use residues for generating process energy (steam and electricity). Chapter 7 highlights improvements in energy production from such residues, most notably the deployment of efficient gasification/combined cycle technology that could strongly improve efficiencies in, for example, pulp and sugar mills. Mitigation potentials reducing the demand for such commodities or raising the recycling rate for paper will not result in additional biomass demand. Biomass can also be used for the production of chemicals and plastics, and as a reducing agent for steel production (charcoal) and for construction purposes (replacing, for example, metals or concrete). Projections for such production routes and subsequent demand for biomass feedstocks are not included in this report, since their deployment is expected to be very limited (see Chapter 7).

In the built environment, biomass is used in particular for heating for both non-commercial uses (and also as cooking fuel) and in modern stoves. The use of biomass for domestic heating could represent a significant mitigation potential. No quantitative estimates are available of future biomass demand for the built environment (for example, heating with pellets or cooking fuels) (Chapter 6).

Biomass supplies

Biomass production on agricultural and degraded lands. Table 11.2 summarizes the biomass supply energy potentials discussed in Chapters 8 (agriculture), 9 (Forestry) and 10 (waste). Those potentials are accompanied by considerable uncertainties. In addition, the estimates are derived from scenarios for the year 2050. The largest contribution could come from energy crops on arable land, assuming that efficiency improvements in agriculture are fast enough to outpace food demand so as to avoid increased pressure on forests and nature areas. Section provides a range from 20–400 EJ. The highest estimate is a technical potential for 2050. Technically, the potentials for such efficiency increases are very large, but the extent to which such potentials can be exploited over time is still poorly studied. Studies assume the successful introduction of biomass production in key regions as Latin America, Sub-Saharan Africa, Eastern Europe and Oceania, combined with gradual improvements in agricultural practice and management (including livestock). However, such development schemes – that could also generate substantial additional income for rural regions that can export biomass – are uncertain, and implementation depends on many factors such as trade policies, agricultural policies, the establishment of sustainability frameworks such as certification, and investments in infrastructure and conventional agriculture (see also Faaij & Domac, 2006).

In addition, the use of degraded lands for biomass production (as in reforestation schemes: 8–110 EJ) could contribute significantly. Although biomass production with such low yields generally results in more expensive biomass supplies, competition with food production is almost absent and various co-benefits, such as the regeneration of soils (and carbon storage), improved water retention, and protection from erosion may also offset some of the establishment costs. An important example of such biomass production schemes at the moment is the establishment of jatropha crops (oil seeds, also spelled jathropa) on marginal lands.

Biomass residues and wastes. Table 11.2 also depicts the energy potentials in residues from forestry (12–74 EJ/yr) and agriculture (15–70 EJ/yr) as well as waste (13 EJ/yr). Those biomass resource categories are largely available before 2030, but also somewhat uncertain. The uncertainty comes from possible competing uses (for example, the increased use of biomaterials such as fibreboard production from forest residues and the use of agro-residues for fodder and fertilizer) and differing assumptions about the sustainability criteria deployed with respect to forest management and agriculture intensity. The current energy potential of waste is approximately 8 EJ/yr, which could increase to 13 EJ in 2030. The biogas fuel potentials from waste, landfill gas and digester gas are much smaller.

Table 11.2: Biomass supply potentials and biomass demand in EJ based on Chapters 4 to 10

Sector Supply Demand 
Biomass supplies to 2050 Energy supply biomass demand 2030 Transport biomass demand 2030 Built environment Industry 
Agriculture       Relevant, in particular in developing countries as cooking fuel Sugar industry significant. Food & beverage industry. No quantitative estimate on use for new biomaterials (e.g. bio-plastics) not significant for 2030. 
Residues 15-70     
Dung 5-55     
Energy crops on arable land and pastures 20-300     
Crops on degraded lands 60-150     
Forestry 12-74 Key application Relevant for second-generation biofuels Relevant   
Waste 13 Power and heat production Possibly via gasification Minimal Cement industry 
Industry Process residues       Relevant; paper & pulp industry 
Total supply primary biomass 125-760         
Total demand primary biomass 70-130 28-43 (electricity) Heat excluded 45-85 Relevant (currently several dozens of EJ; additional demand may be limited) Significant demand; paper & pulp and sugar industry use own process residues; additional demand expected to be limited 

Synthesis of biomass supply & demand

A proper comparison of demand and supply is not possible since most of the estimates for supply relate to 2050. Demand has been assessed for 2030. Taking this into account, the lower end of the biomass supply (estimated at about 125 EJ/yr) exceeds the lower estimate of biomass demand (estimated at 70 EJ/yr). However, demand does not include estimates of domestic biomass use (such as cooking fuel, although that use may diminish over time depending on development pathways in developing countries), increased biomass for production of heat (although additional demand in this area may be limited) and biomass use in industry (excluding the possible demand of biomass for new biomaterials). It seems that this demand can be met by biomass residues from forestry, agriculture, waste and dung and a limited contribution from energy crops. Such a ‘low biomass demand’ pathway may develop from the use of agricultural crops with more limited potentials, lower GHG mitigation impact and less attractive economic prospects, in particular in temperate climate regions. The major exception here is sugar-cane-based ethanol production.

The estimated high biomass demand consists of an estimated maximum use of biomass for power production and the constrained growth of production of biofuels when the WEO projections are taken into consideration (25 EJ/yr biofuels and about 40 EJ/yr primary biomass demand). Total combined demand for biomass for power and fuels adds up to about 130 EJ/yr. Clearly, a more substantial contribution from energy crops (perhaps in part from degraded lands, for example producing jatropha oil seeds) is required to cover total demand of this magnitude, but this still seems feasible, even for 2030; the low-end estimate for energy crops for agricultural land is 50 EJ/yr, which is in line with the 40 EJ/yr primary projected demand for biofuels.

However, as was also acknowledged in the WEO, the demand for biomass as biofuels in around 2030 will depend in particular on the commercialization of second-generation biofuel technologies (i.e. the large-scale gasification of biomass for the production of synfuels as Fischer-Tropsch diesel, methanol or DME, and the hydrolysis of lignocellulosic biomass for the production of ethanol). According to Hamelinck and Faaij (2006), such technologies offer competitive biofuel production compared to oil priced at between 40–50 US$/barrel (assuming biomass prices of around 2 US$/GJ). In Chapter 5, Figure 5.9 (IEA, 2006b), however, assumes higher biofuel costs. Another key option is the wider deployment of sugar cane for ethanol production, especially on a larger scale using state-of-the art mills, and possibly in combination with hydrolysis technology and additional ethanol production from bagasse (as argued by Moreira, 2006 and other authors). The availability of such technologies before 2020 may lead to an acceleration of biofuel production and use, even before 2030. Biofuels may therefore become the most important demand factor for biomass, especially in the longer term (i.e. beyond 2030).

A more problematic situation arises when the development of biomass resources (both residues and cultivated biomass) fails to keep up with demand. Although the higher end of biomass supply estimates (2050) is well above the maximum projected biomass demand for 2030, the net availability of biomass in 2030 will be considerably lower than the 2050 estimates. If biomass supplies fall short, this is likely to lead to significant price increases for raw materials. This would have a direct effect on the economic feasibility of various biomass applications. Generally, biomass feedstock costs can cover 30–50% of the production costs of secondary energy carriers, so increasing feedstock prices will quickly reduce the increase in biomass demand (but simultaneously stimulate investments in biomass production). To date, there has been very little research into interactions of this kind, especially at the global scale.

Comparing mitigation estimates for top-down and bottom-up modelling is not straightforward. Bottom-up mitigation responses are typically more detailed and derived from more constrained modelling exercises. Cost estimates are therefore in partial equilibrium in that input and output market prices are fixed, as may be key input quantities such as acreage or capital. Top-down mitigation responses consider more generic mitigation technologies and changes in outputs and inputs (such as shifts from food crops or forests to energy crops) as well as changes in market prices (such as land prices as competition for land increases). In addition, current top-down models optimistically assume the simultaneous global adoption of a coordinated climate policy with an unconstrained, or almost unconstrained, set of mitigation options across sectors. A review of top-down studies (Chapter 3 data assembled from Rose et al. (2007) and US CCSP (2006)) results in a range for total projected biomass use over all cost categories of 20 to 79 EJ/yr (defined as solid and liquid, requiring a conversion ratio from primary biomass to fuels). This is, on average, half the range for estimates obtained via bottom-up information from the various chapters.

Given the relatively small number of relevant scenario studies available to date, it is fair to say that the role of biomass in long-term stabilization (beyond 2030) will be very significant but that it is subject to relatively large uncertainties. Further research is required to improve our insight into the potential. A number of key factors influencing biomass mitigation potential are worth noting: the baseline economic growth and energy supply alternatives, assumptions about technological change (such as the rate of development of cellulosic ethanol conversion technology), land use competition, and mitigation alternatives (overall and land-related).

Given the lack of studies of how biomass resources may be distributed over various demand sectors, we do not suggest any allocation of the different biomass supplies to various applications. Furthermore, the net avoidance costs per ton of CO2 of biomass usage depend on a wide variety of factors, including the biomass resource and supply (logistics) costs, conversion costs (which in turn depend on the availability of improved or advanced technologies) and reference fossil fuel prices, most notably of oil.