Editing IPCC:AR6/WGIII/Chapter-7 (section)

=== 7.4.4 Bioenergy and BECCS ===

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'''Activities, co-benefits, risks and implementation opportunities and barriers''' '''.''' Bioenergy refers to energy products (solid, liquid and gaseous fuels, electricity, heat) derived from multiple biomass sources including organic waste, harvest residues and by-flows in the agriculture and forestry sectors, and biomass from tree plantations, agroforestry systems, lignocellulosic crops, and conventional food/feed crops. It may reduce net GHG emissions by displacing the use of coal, oil and natural gas with renewable biomass in the production of heat, electricity, and fuels. When combined with carbon capture and storage (BECCS) and biochar production, bioenergy systems may provide CDR by durably storing biogenic carbon in geological, terrestrial, or ocean reservoirs, or in products, further contributing to mitigation ( [[#Chum--2011|Chum et al. 2011]] ; [[#Cabral--2019|Cabral et al. 2019]] ; [[#Hammar--2020|Hammar and Levihn 2020]] ; [[#Emenike--2020|Emenike et al. 2020]] ; [[#Moreira--2020b|Moreira et al. 2020b]] ; Y. [[#Wang--2020|Wang et al. 2020]] : [[#Johnsson--2020|Johnsson et al. 2020]] ) ( [[#7.4.3.2|Section 7.4.3.2]] , Chapters 3, 4, 6 and 12).

This section addresses especially aspects related to land use and biomass supply for bioenergy and BECCS. The mitigation potential presented here and in Table 7.3, includes only the CDR component of BECCS. The additional mitigation achieved from displacing fossil fuels is covered elsewhere (Chapters 6, 8, 9, 10, 11 and 12).

Modern bioenergy systems (as opposed to traditional use of fuelwood and other low-quality cooking and heating fuels) currently provide approximately 30 EJ yr –1 of primary energy, making up 53% of total renewable primary energy supply ( [[#IEA--2019|IEA 2019]] ). Bioenergy systems are commonly integrated within forest and agriculture systems that produce food, feed, lumber, paper and other bio-based products. They can also be combined with other AFOLU mitigation options: deployment of energy crops, agroforestry and A/R can provide biomass while increasing land carbon stocks (Sections 7.4.2.2 and 7.4.3.3) and anaerobic digestion of manure and wastewater, to reduce methane emissions, can produce biogas and CO 2 for storage ( [[#7.4.3.7|Section 7.4.3.7]] ). But ill-deployment of energy crops can also cause land carbon losses ( [[#Hanssen--2020|Hanssen et al. 2020]] ) and increased biomass demand for energy could hamper other mitigation measures such as reduced deforestation and degradation (Sections 7.4.2.1).

Bioenergy and BECCS can be associated with a range of co-benefits and adverse side effects ( [[#Smith--2016|Smith et al. 2016]] ; [[#Jia--2019|Jia et al. 2019]] ; [[#Calvin--2021|Calvin et al. 2021]] ) ( [[IPCC:Wg3:Chapter:Chapter-12#12.5|Section 12.5]] ). It is difficult to disentangle bioenergy development from the overall development in the AFOLU sector given its multiple interactions with food, land, and energy systems. It is therefore not possible to precisely determine the scale of bioenergy and BECCS deployment at which negative impacts outweigh benefits. Important uncertainties include governance systems, future food and biomaterials demand, land-use practices, energy systems development, climate impacts, and time scale considered when weighing negative impacts against benefits ( [[#Robledo-Abad--2017|Robledo-Abad et al. 2017]] ; [[#Turner--2018b|Turner et al. 2018b]] ; [[#Daioglou--2019|Daioglou et al. 2019]] ; [[#Wu--2019|Wu et al. 2019]] ; [[#Kalt--2020|Kalt et al. 2020]] ; [[#Hanssen--2020|Hanssen et al. 2020]] ; [[#Calvin--2021|Calvin et al. 2021]] ; [[#Cowie--2021|Cowie et al. 2021]] ) (SRCCL, Cross-Chapter Box 7; Box 7.7). The use of municipal organic waste, harvest residues, and biomass processing by-products as feedstock is commonly considered to have relatively lower risk, provided that associated land-use practices are sustainable ( [[#Cowie--2021|Cowie et al. 2021]] ). Deployment of dedicated biomass production systems can have positive and negative implications on mitigation and other sustainability criteria, depending on location and previous land use, feedstock, management practice, deployment strategy and scale ( [[#Rulli--2016|Rulli et al. 2016]] ; [[#Popp--2017|Popp et al. 2017]] ; [[#Daioglou--2017|Daioglou et al. 2017]] ; [[#Staples--2017|Staples et al. 2017]] ; [[#Carvalho--2017|Carvalho et al. 2017]] ; [[#Humpenöder--2018|Humpenöder et al. 2018]] ; [[#Fujimori--2019|Fujimori et al. 2019]] ; [[#Hasegawa--2020|Hasegawa et al. 2020]] ; [[#Drews--2020|Drews et al. 2020]] ; [[#Schulze--2020|Schulze et al. 2020]] ; [[#Stenzel--2020|Stenzel et al. 2020]] ; [[#Mouratiadou--2020|Mouratiadou et al. 2020]] ; [[#Buchspies--2020|Buchspies et al. 2020]] ; [[#Hanssen--2020|Hanssen et al. 2020]] , [[#IPBES--2019b|IPBES 2019b]] ) (Sections 12.5 and 17.3.3.1).

'''Conclusions from AR5 and IPCC Special Reports (SR1.5, SROCC and SRCCL); mitigation potential, costs, and pathways.''' Many more stringent mitigation scenarios in AR5 relied heavily on bioenergy and BECCS. The SR1.5 reported a range for the CDR potential of BECCS (2100) at 0.5 to 5 GtCO 2 -eq yr –1 when applying constraints reflecting sustainability concerns, at a cost of 100–200 USD tCO 2 –1 ( [[#Fuss--2018|Fuss et al. 2018]] ). The SRCCL reported a technical CDR potential for BECCS at 0.4–11.3 GtCO 2 yr –1 ( ''medium confidence'' ), noting that most estimates do not include socio-economic barriers, the impacts of future climate change, or non-GHG climate forcing (IPCC. 2019). The SR1.5 and SRCCL highlighted that bioenergy and BECCS can be associated with multiple co-benefits and adverse side effects that are context specific.

'''Developments since AR5 and IPCC Special Reports (SR1.5, SROCC and SRCCL).''' The role of bioenergy and BECCS in mitigation pathways has been reduced as IAM-based studies have incorporated broader mitigation portfolios and have explored non-CO 2 emissions reduction and a wider variation of underlying assumptions about socio-economic drivers and associated energy and food demand, as well as deployment limits such as land availability for A/R and for cultivation of crops used for bioenergy and BECCS ( [[#Grubler--2018|Grubler et al. 2018]] ; Van Vuuren et al. 2018).

Increased availability of spatially explicit data and advances in the modelling of crop productivity and land use, land carbon stocks, hydrology, and ecosystem properties, have enabled more comprehensive analyses of factors that influence the contribution of bioenergy and BECCS in IAM-based mitigation scenarios, and also associated co-benefits and adverse side effects (Turner et al.2018a; [[#Wu--2019|Wu et al. 2019]] , [[#Li--2020|Li et al. 2020]] , [[#Hanssen--2020|Hanssen et al. 2020]] ; [[#Drews--2020|Drews et al. 2020]] ; [[#Ai--2021|Ai et al. 2021]] ; [[#Hasegawa--2021|Hasegawa et al. 2021]] ). Yet, IAMs are still coarse in local land-use practices. ( [[#Daioglou--2019|Daioglou et al. 2019]] ; [[#Wu--2019|Wu et al. 2019]] ; [[#Moreira--2020b|Moreira et al. 2020b]] ). Literature complementary to IAM studies indicate opportunities for integration of biomass production systems into agricultural landscapes (e.g., agroforestry, double cropping) to produce biomass while achieving co-benefits ( [[IPCC:Wg3:Chapter:Chapter-12#12.5|Section 12.5]] ). Similarly, climate-smart forestry puts forward measures (Box 7.3) adapted to regional circumstances in forest sectors, enabling co-benefits in nature conservation, soil protection, employment and income generation, and provision of wood for buildings, bioenergy and other bio-based products ( [[#Nabuurs--2017|Nabuurs et al. 2017]] ).

Studies have also investigated the extent and possible use of marginal, abandoned, and degraded lands, and approaches to help restore the productive value of these lands ( [[#Awasthi--2017|Awasthi et al. 2017]] ; [[#Fritsche--2017|Fritsche et al. 2017]] ; Chiaramonti and Panoutsou, 2018; [[#Fernando--2018|Fernando et al. 2018]] ; Elbersen et al. 2019; [[#Rahman--2019|Rahman et al. 2019]] ; [[#Næss--2021|Næss et al. 2021]] ). In the SRCCL, the presented range for degraded or abandoned land was 32–1400 Mha ( [[#Jia--2019|Jia et al. 2019]] ). Recent regional assessments not included in the SRCCL found up to 69 Mha in EU-28, 185 Mha in China, 9.5 Mha in Canada, and 127 Mha in the USA ( [[#Emery--2017|Emery et al. 2017]] ; [[#Liu--2017|Liu et al. 2017]] ; Elbersen et al. 2019; Zhang et al.2020; [[#Vera--2021|Vera et al. 2021]] ). The definitions of marginal/abandoned/degraded land, and the methods used to assess such lands remain inconsistent across studies ( [[#Jiang--2019|Jiang et al. 2019]] ), causing large variation amongst them ( [[#Jiang--2021|Jiang et al. 2021]] ). Furthermore, the availability of such lands has been contested since they may serve other functions, such as: subsistence, biodiversity protection, and so on ( [[#Baka--2014|Baka 2014]] ).

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