Biomass residues as twenty-first century bioenergy feedstock—a comparison of eight integrated assessment models

In the twenty-first century, modern bioenergy could become one of the largest sources of energy, partially replacing fossil fuels and contributing to climate change mitigation. Agricultural and forestry biomass residues form an inexpensive bioenergy feedstock with low greenhouse gas (GHG) emissions, if harvested sustainably. We analysed quantities of biomass residues supplied for energy and their sensitivities in harmonised bioenergy demand scenarios across eight integrated assessment models (IAMs) and compared them with literature-estimated residue availability. IAM results vary substantially, at both global and regional scales, but suggest that residues could meet 7–50% of bioenergy demand towards 2050, and 2–30% towards 2100, in a scenario with 300 EJ/year of exogenous bioenergy demand towards 2100. When considering mean literature-estimated availability, residues could provide around 55 EJ/year by 2050. Inter-model differences primarily arise from model structure, assumptions, and the representation of agriculture and forestry. Despite these differences, drivers of residues supplied and underlying cost dynamics are largely similar across models. Higher bioenergy demand or biomass prices increase the quantity of residues supplied for energy, though their effects level off as residues become depleted. GHG emission pricing and land protection can increase the costs of using land for lignocellulosic bioenergy crop cultivation, which increases residue use at the expense of lignocellulosic bioenergy crops. In most IAMs and scenarios, supplied residues in 2050 are within literature-estimated residue availability, but outliers and sustainability concerns warrant further exploration. We conclude that residues can cost-competitively play an important role in the twenty-first century bioenergy supply, though uncertainties remain concerning (regional) forestry and agricultural production and resulting residue supply potentials. © 2019, The Author(s)

The global mismatch between equitable carbon dioxide removal liability and capacity

Limiting climate change to 1.5°C and achieving net-zero emissions would entail substantial carbon dioxide removal (CDR) from the atmosphere by the mid-century, but how much CDR is needed at country level over time is unclear. The purpose of this paper is to provide a detailed description of when and how much CDR is required at country level in order to achieve 1.5°C and how much CDR countries can carry out domestically. We allocate global CDR pathways among 170 countries according to 6 equity principles and assess these allocations with respect to countries’ biophysical and geophysical capacity to deploy CDR. Allocating global CDR to countries based on these principles suggests that CDR will, on average, represent ∼4% of nations’ total emissions in 2030, rising to ∼17% in 2040. Moreover, equitable allocations of CDR, in many cases, exceed implied land and carbon storage capacities. We estimate ∼15% of countries (25) would have insufficient land to contribute an equitable share of global CDR, and ∼40% of countries (71) would have insufficient geological storage capacity. Unless more diverse CDR technologies are developed, the mismatch between CDR liabilities and land-based CDR capacities will lead to global demand for six GtCO2 carbon credits from 2020 to 2050. This demonstrates an imperative demand for international carbon trading of CDR

The global mismatch between equitable carbon dioxide removal liability and capacity

Limiting climate change to 1.5°C and achieving net-zero emissions would entail substantial carbon dioxide removal (CDR) from the atmosphere by mid-century, but how much CDR is needed at country level over time is unclear. The purpose of this paper is to provide a detailed description of when and how much CDR is required at country level to take in order to achieve 1.5°C and how much CDR countries can carry out domestically. We allocate global CDR pathways among 170 countries according to six equity principles and assess these allocations with respect to countries' biophysical and geophysical capacity to deploy CDR. Allocating global CDR to countries based on these principles suggests that CDR will, on average, represent ∼4% of nations' total emissions in 2030, rising to ∼17% in 2040. Moreover, equitable allocations of CDR, in many cases, exceed implied land and carbon storage capacities. We estimate ∼15% of countries (25) would have insufficient land to contribute an equitable share of global CDR, and ∼40% of countries (71) would have insufficient geological storage capacity. Unless more diverse CDR technologies are developed, the mismatch between CDR liabilities and land-based CDR capacities will lead to global demand for 6 GtCO2 carbon credits from 2020 to 2050. This demonstrates an imperative demand for international carbon trading of CDR

The many greenhouse gas footprints of green hydrogen

Green hydrogen could contribute to climate change mitigation, but its greenhouse gas footprint varies with electricity source and allocation choices. Using life-cycle assessment we conclude that if electricity comes from additional renewable capacity, green hydrogen outperforms fossil-based hydrogen. In the short run, alternative uses of renewable electricity likely achieve greater emission reductions

Global implications of crop-based bioenergy with carbon capture and storage for terrestrial vertebrate biodiversity

Bioenergy with carbon capture and storage (BECCS) based on purpose‐grown lignocellulosic crops can provide negative CO(2) emissions to mitigate climate change, but its land requirements present a threat to biodiversity. Here, we analyse the implications of crop‐based BECCS for global terrestrial vertebrate species richness, considering both the land‐use change (LUC) required for BECCS and the climate change prevented by BECCS. LUC impacts are determined using global‐equivalent, species–area relationship‐based loss factors. We find that sequestering 0.5–5 Gtonne of CO(2) per year with lignocellulosic crop‐based BECCS would require hundreds of Mha of land, and commit tens of terrestrial vertebrate species to extinction. Species loss per unit of negative emissions decreases with: (i) longer lifetimes of BECCS systems, (ii) less overall deployment of crop‐based BECCS and (iii) optimal land allocation, that is prioritizing locations with the lowest species loss per negative emission potential, rather than minimizing overall land use or prioritizing locations with the lowest biodiversity. The consequences of prevented climate change for biodiversity are based on existing climate response relationships. Our tentative comparison shows that for crop‐based BECCS considered over 30 years, LUC impacts on vertebrate species richness may outweigh the positive effects of prevented climate change. Conversely, for BECCS considered over 80 years, the positive effects of climate change mitigation on biodiversity may outweigh the negative effects of LUC. However, both effects and their interaction are highly uncertain and require further understanding, along with the analysis of additional species groups and biodiversity metrics. We conclude that factoring in biodiversity means lignocellulosic crop‐based BECCS should be used early to achieve the required mitigation over longer time periods, on optimal biomass cultivation locations, and most importantly, as little as possible where conversion of natural land is involved, looking instead to sustainably grown or residual biomass‐based feedstocks and alternative strategies for carbon dioxide removal

Life cycle greenhouse gas benefits or burdens of residual biomass from landscape management

The use of residual biomass for the production of bioenergy and biomaterials is often suggested as a strategy to avoid negative effects associated with dedicated biomass production. One potential source is biomass from landscape management. The goal of this study was to find the lowest net greenhouse gas (GHG) emissions of various applications of residual biomass from landscape management. GHG balances of thirteen residual biomass applications were calculated and compared to their respective conventional counterfactuals. As a case study, the potential contribution to climate change mitigation through the use of residual biomass available from vegetation management in floodplains of the Dutch Rhine delta were quantified. The greatest GHG benefits are achieved when using woody biomass to produce heat (−132 kg CO 2 -eq./tonne wet biomass) and grassy biomass to produce growth media (−229 kg CO 2 -eq./tonne wet biomass). In contrast, composting grassy biomass for fertiliser replacement on agricultural fields results in the largest GHG burdens of 62 kg CO 2 -eq./tonne wet biomass. The findings imply that residual biomass from landscape management can contribute to both GHG benefits and burdens, depending on the application. Higher benefits were found for bioenergy than for biomaterial applications. Biomass applications should be chosen with care and consideration of their counterfactuals

Life cycle greenhouse gas benefits or burdens of residual biomass from landscape management

The use of residual biomass for the production of bioenergy and biomaterials is often suggested as a strategy to avoid negative effects associated with dedicated biomass production. One potential source is biomass from landscape management. The goal of this study was to find the lowest net greenhouse gas (GHG) emissions of various applications of residual biomass from landscape management. GHG balances of thirteen residual biomass applications were calculated and compared to their respective conventional counterfactuals. As a case study, the potential contribution to climate change mitigation through the use of residual biomass available from vegetation management in floodplains of the Dutch Rhine delta were quantified. The greatest GHG benefits are achieved when using woody biomass to produce heat (−132 kg CO 2 -eq./tonne wet biomass) and grassy biomass to produce growth media (−229 kg CO 2 -eq./tonne wet biomass). In contrast, composting grassy biomass for fertiliser replacement on agricultural fields results in the largest GHG burdens of 62 kg CO 2 -eq./tonne wet biomass. The findings imply that residual biomass from landscape management can contribute to both GHG benefits and burdens, depending on the application. Higher benefits were found for bioenergy than for biomaterial applications. Biomass applications should be chosen with care and consideration of their counterfactuals

Worldwide greenhouse gas emissions of green hydrogen production and transport

Large-scale introduction of green hydrogen is envisioned to play an important role in reaching net-zero greenhouse gas emissions. The production and transport of green hydrogen itself is, however, not free from emissions. Here we assess the life-cycle greenhouse gas emissions for 1,025 planned green hydrogen facilities, covering different electrolyser technologies and renewable electricity sources in 72 countries. We demonstrate that the current exclusion of life-cycle emissions of renewables, component manufacturing and hydrogen leakage in regulations gives a false impression that green hydrogen can easily meet emission thresholds. Evaluating different hydrogen production configurations, we find median production emissions in the most optimistic configuration of 2.9 kg CO2 equivalents (CO2e) kg H2−1 (0.8–4.6 kgCO2e kg H2−1, 95% confidence interval). Including 1,000 km transport via pipeline or liquid hydrogen shipping adds another 1.5 or 1.8 kgCO2e kg H2−1, respectively. We conclude that achieving low-emission green hydrogen at scale requires well-chosen production configurations with substantial emission reductions along the supply chain.</p

Biomass residues as twenty-first century bioenergy feedstock—a comparison of eight integrated assessment models

In the twenty-first century, modern bioenergy could become one of the largest sources of energy, partially replacing fossil fuels and contributing to climate change mitigation. Agricultural and forestry biomass residues form an inexpensive bioenergy feedstock with low greenhouse gas (GHG) emissions, if harvested sustainably. We analysed quantities of biomass residues supplied for energy and their sensitivities in harmonised bioenergy demand scenarios across eight integrated assessment models (IAMs) and compared them with literature-estimated residue availability. IAM results vary substantially, at both global and regional scales, but suggest that residues could meet 7–50% of bioenergy demand towards 2050, and 2–30% towards 2100, in a scenario with 300 EJ/year of exogenous bioenergy demand towards 2100. When considering mean literature-estimated availability, residues could provide around 55 EJ/year by 2050. Inter-model differences primarily arise from model structure, assumptions, and the representation of agriculture and forestry. Despite these differences, drivers of residues supplied and underlying cost dynamics are largely similar across models. Higher bioenergy demand or biomass prices increase the quantity of residues supplied for energy, though their effects level off as residues become depleted. GHG emission pricing and land protection can increase the costs of using land for lignocellulosic bioenergy crop cultivation, which increases residue use at the expense of lignocellulosic bioenergy crops. In most IAMs and scenarios, supplied residues in 2050 are within literature-estimated residue availability, but outliers and sustainability concerns warrant further exploration. We conclude that residues can cost-competitively play an important role in the twenty-first century bioenergy supply, though uncertainties remain concerning (regional) forestry and agricultural production and resulting residue supply potentials

The potential of emerging bio-based products to reduce environmental impacts

Abstract The current debate on the sustainability of bio-based products questions the environmental benefits of replacing fossil- by bio-resources. Here, we analyze the environmental trade-offs of 98 emerging bio-based materials compared to their fossil counterparts, reported in 130 studies. Although greenhouse gas life cycle emissions for emerging bio-based products are on average 45% lower (−52 to −37%; 95% confidence interval), we found a large variation between individual bio-based products with none of them reaching net-zero emissions. Grouped in product categories, reductions in greenhouse gas emissions ranged from 19% (−52 to 35%) for bioadhesives to 73% (−84 to −54%) for biorefinery products. In terms of other environmental impacts, we found evidence for an increase in eutrophication (369%; 163 to 737%), indicating that environmental trade-offs should not be overlooked. Our findings imply that the environmental sustainability of bio-based products should be evaluated on an individual product basis and that more radical product developments are required to reach climate-neutral targets