Matching bioenergy supply and energy demand in Germany
The analysis of Fehrenbach et al. (2019) follows a bottom-up approach. They do not question whether the potential quantities of the most suitable target uses assigned based on a list of criteria are also in demand there to the same extent. Nor are these prioritised utilisation pathways aligned with the scenarios for a Resource-Efficient and Greenhouse-Gas-Neutral Germany (RTD) or the long-term and climate change scenarios for Germany (Pfluger, Tersteegen & Franke 2017).
After the completion of the study, we now examined how the energy sources allocated to the utilisation pathways correspond to the demand in these sectors. Figure 24.2 shows that both the demand for industrial process heat and aviation fuel is significantly higher than the supply that can be covered by biomass. The metal industry alone requires approximately 550 PJ of process heat at high or medium temperature. The chemical industry has a demand of about 360 PJ (Pfluger et al. 2017). Biomass is an attractive option for industry to avoid greenhouse gases. It allows heat to be transferred to a relatively high temperature level (depending on the calorific value), as well as being available in various aggregate states.
The role of biomass in forward-looking scenario studies
Biomass plays a vital role in most forward-looking scenario studies using energy systems models such as Pfluger et al. (2017), Gerhardt et al. (2015) or
Figure 24.2 Comparing the useful energy from available potential of biogenic waste and residues with the current demand of heat, electricity and transport fuel. Baseline: biomass allocated according to the evaluation by five criteria (see text); sensitivity: evaluation without the criteria production costs.
Source: own illustration based on data from Fehrenbach et al. (2019), Pfluger et al. (2017), AG Energiebilanzen e.V. (2019).
Repenning et al. (2015). These studies differ in terms of underlying biomass potentials (biogenic waste and residues, available land for the cultivation of dedicated crops as well as the amount of biomass imports) and biomass allocation to the various sectors. In Gunther et al. (2019), no use at all of the dedicated crops is foreseen in the future (see also Chapters 12 and 13 of this volume). All studies conclude that biomass should primarily be used in those sectors where there are no or few affordable alternatives for decarbonisation, respectively defossilisation. Most often, aviation and shipping, as well as high-temperature heat for industrial processes, are mentioned as the main future applications. But also the chemical industry must not be neglected which needs a renewable carbon source in the future This could either be recycled carbon via PtG/PtL (especially for short chain-length molecules) or biomass, from which longer, more complex molecules synthesised by nature could be obtained.
Conclusions
The role of biomass in a future without fossil CO2 emissions is complex. On the one hand, biomass is a readily available resource and should also be used within the framework of a resource-efficient economy. On the other hand.
biomass potentials are limited by various factors. Biomass production is linked to land area, which — given the growing world population — must be used for food supply first. For this reason, the potential for non-food uses of biomass from dedicated crops will always be sharply limited.
Yet, there is a potential of dedicated crops from marginal land or surplus land with low risk for indirect land-use change (iLUC). As these land categories have not yet been clearly defined, data on potentially available areas are therefore not comparable. In addition, conflicts with biodiversity often arise when these types of land are used. Moreover, the yields from marginal areas are marginal. The realisation of greater potential for the use of these areas is therefore not to be expected.
The question of how much forest wood is available is a particularly complex one: even the distinction between wood as the actual harvested good and what is called residual forest wood is unclear. The decisive factor is the forestry strategy: is the forest rather a production site for maximised wood yield or a near-natural ecosystem with high carbon storage? If priority is given to the second option, the potential for use is also significantly lower here. Besides, there are the imponderables of forest restructuring and climate change, which may result in a high volume of timber in the short term. The long-term potential may continue to decline.
Among the multitude of different biogenic wastes and residues, straw accounts for the largest unused energy potential to date. The more recent studies estimate this at a range of 140 to 200 Petajoules. Manure also offers the possibility of expanding the production of biogas. Otherwise, the majority of substances are already used for energy.
On the way to a climate-neutral world, biomass thus makes a contribution to directly replacing fossil fuels. The results presented here on the potentials of biogenic waste and residues as well as of cultivated biomass on unused and surplus land show that it is difficult to increase the domestic biomass supply compared to today. According to most forward-looking scenario studies, the future biomass demand for energy in the sectors transport (aviation and marine fuels) and industry (high-temperature heat) will remain high or even rise. Besides these, the demand for biomass for material use, e.g. in the chemical industry, could continue to rise. It is clear that biomass demand will exceed domestic biomass supply, so significant biomass imports may be necessary. Alternatively, the demand for hydrocarbons for fuels and chemicals could also be met by PtG/PtL technologies, but at significantly higher costs (also in the future). Biomass should, therefore, be used in particular where there are no, or only a few, very expensive renewable alternatives available. To answer this question, further research activities are needed to determine more precisely the future role of biomass in a defossilised world.
