Societal techno-economic assessment of biochar in sustainable land use with targeted applications

Abstract

This dissertation presents the societal techno-economic assessment (TEA) methodology, a novel integration of the life cycle assessment (LCA) and TEA methodologies through monetizing the LCA results. It does so for a case study of biochar, a biobased carbon dioxide removal (CDR) technology. Increasingly, the global environment is being put under pressure. The planetary boundaries framework represents limits for nine of Earth’s biophysical subsystems and processes that should not be crossed to avoid unacceptable environmental change. In the latest update, six of those have been transgressed. One of these is the one concerning climate change, which is arguably the one most talked about. To limit warming to 2°C, immediate reductions in greenhouse gas (GHG) emissions and active removal of CO2 from the atmosphere through CDR technologies are needed. One such technology is biochar, the carbonaceous product of biomass pyrolysis. Pyrolysis is the thermochemical conversion process happening in the absence of oxygen. When applied to soil, biochar can have many benefits, such as increased water-holding capacity and reduced nutrient leaching. These other benefits help reduce pressure on other planetary boundaries (i.e., freshwater change and biogeochemical flows). Even though biochar is often considered one product, it is variable and versatile. Its variability stems from the fact that its properties can be altered by changing feedstock and production conditions. Biochar’s versatility refers to the fact that it has many possible applications. When deploying novel technologies such as biochar, the multitude of environmental concerns call for integrated sustainability assessments. After an introduction in Chapter 1, the second chapter of this dissertation lays the foundation of the work through a systematic review of the available literature regarding biochar economics. In this chapter, the terms profitability and desirability are distinguished. Profitability means private benefits outweigh private costs, whereas desirability accounts for private and external costs and benefits. This review found that biochar's economic performance is highly case-specific, depending on factors such as location, feedstock, scale, pyrolysis conditions, biochar price, and the inclusion of externalities. The latter relates to this review's second aim: to determine to what extent external costs and benefits have been included. Existing research includes externalities to some extent but mostly focuses on the external benefits rather than the external costs. Furthermore, the focus is on externalities related to GHG emissions (i.e., biochar's climatemitigating potential). Chapter 3 presents the first step towards integrating externalities into the TEA framework by quantifying the environmental externalities using an LCA. Whereas there was no focus on specific feedstocks in Chapter 2, the LCA was carried out for two types of biomass. These are the woody fraction of green waste and chicken manure pellets, chosen with BASTA project partners for their relevance in Flanders and for being distinctly different (i.e., wood and manure). Furthermore, both are studied when pyrolyzed at 450°C and 600°C and in two applications. The applications are direct use as a soil amendment or a cascading use where it is first used in anaerobic digestion. Building on a research gap identified in the systematic review (i.e., that externalities other than those related to climate change should be included), this LCA set out to study all impact categories. Under the assumptions in the study, the biochars from both feedstocks provided environmental benefits for some impact categories. However, no option outperforms all others for all impact categories. The LCA further concluded that the environmental impact of biochar is greatly driven by the market substitution effects (i.e., fertilizer and energy). Chapter 4 presents the societal TEA framework, which is the novel integration of LCA and TEA methodologies through monetizing the LCA results. This monetization is a way to weight the LCA results, thereby enabling easier decisionmaking, given that, in the previous chapter, no option outperforms all others for all impact categories. This easier decision-making for businesses and policymakers is a main advantage of this monetized approach, not just for the different impact categories in the LCA but also for integrating the different sustainability pillars. Furthermore, monetization allows us to do so intuitively, speaking the language of businesses and policymakers. Furthermore, similar to a traditional TEA and building upon its foundation, the societal TEA involves a dynamic integration of technological and economic parameters, enabling continuous data updates and automatic recalculations. This characteristic distinguishes the societal TEA framework from other methods, where such dynamic integration is possible but not an explicit aim, as it is within the TEA family of methodologies. The societal TEA measures profitability with the private Net Present Value (NPV) and desirability with the societal NPV. These metrics can be directly compared to determine whether government intervention is justifiable, another key advantage of the societal TEA methodology. Government intervention is justifiable whenever societal (i.e., private and external) benefits outweigh societal costs. The most important limitation of this dissertation is the omission of social impacts. These were left out because both their quantification and monetization are still in the early stages of development. Future research should aim to include the social pillar of sustainability to bring about a true societal TEA. Nonetheless, the case study for biochar presented in this chapter serves as a useful illustration of the societal TEA framework. The following can be said based on including environmental externalities and considering the specific situation at hand. Biochar production from the woody fraction of green waste is profitable when the biochar selling price is about €500/Mg. This biochar shows negligible externalities in direct field application but provides net external benefits when used in a cascade of applications. Even at a biochar selling price of €0/Mg, there is about a 50% probability of this cascading use to be desirable. Given the high purchasing price of chicken manure pellets, high biochar selling prices (i.e., €1,400/Mg for biochar produced at 450°C and €1,600/Mg at 600°C) are required for profitability. Even including externalities for the scenarios with cascading use, which are the scenarios with the highest net external benefits, a biochar selling price of €600/Mg (450°C) or €650/Mg (600°C) is required. Finally, general conclusions and recommendations for future research are presented in the fifth chapter. This chapter also includes suggestions on how the results of this dissertation could be valorized.