Editing IPCC:AR6/WGIII/Chapter-12 (section)

=== 12.2.2 Costs and Potentials of Options for 2030 ===

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In this section, we present an overview of mitigation options per sector. An overview of net emissions reduction potentials for different mitigation options is presented in Table 12.3.

'''Table 12.3 | Detailed overview of global net GHG emissions reduction potentials (GtCO''' 2 '''-eq) in the various cost categories for the year 2030.''' Note that potentials within and across sectors cannot be summed, as the adoption of some options may affect the mitigation potentials of other options. Only monetary costs and benefits of options are taken into account. Negative costs occur when the benefits are higher than the costs. For wind energy, for example, this is the case if production costs are lower than those of the fossil alternatives. Ranges are indicated for each option separately, or indicated for the sector as a whole (see Notes column); they reflect full ranges. Cost ranges are not cumulative, e.g., to obtain the full potential below USD50 tCO 2 -eq –1 , the potentials in the cost bins &lt;USD0, USD0–20 and USD20–50 tCO 2 -eq –1 need to be summed together.

{| class="wikitable"
|-
! rowspan="2"| '''Emissions reduction options (including carbon sequestration options)'''

! colspan="5"| '''Cost categories (USD tCO''' 2 '''-eq''' –1 ''')'''

! rowspan="2"| '''Notes'''

|-
! '''&lt;0'''

! '''0–20'''

! '''20–50'''

! '''50–100'''

! '''100–200'''

|-
| colspan="6"| '''Energy sector'''

| '''Cost ranges are derived as ranges of LCOEs for different electricity generating technologies and the potentials are updated from [[#UNEP--2017|UNEP (2017)]] .'''

|-
| Wind energy

| colspan="3"| 2.1–5.6

(majority in &lt;0 range)

|
| rowspan="2"| Costs for system integration of intermittent renewables are not included, but these are expected to have limited impact until 2030 and will depend on market design and cross-sectoral integration.

|-
| Solar energy

| colspan="4"| 2.0–7.0

(majority in &lt;0 range)

|
|-
| Nuclear energy

| colspan="5"| 0.88 ± 50%

|
|-
| Bioelectricity

|
| colspan="2"|
| colspan="2"| 0.86 ± 50%

| Biomass use for indoor heating and industrial heat is not included here. Currently, about 90% of renewable industrial heat consumption is bio-based, mainly in industries that can use their own biomass waste and residues (IEA, 2020).

|-
| Hydropower

|
| colspan="3"| 0.32 ± 50%

|
| Mitigation costs show large variation and may end up beyond these ranges.

|-
| Geothermal energy

|
| colspan="3"| 0.74 ± 50%

|
| Mitigation costs show large variation and may end up beyond these ranges.

|-
| Carbon capture and storage (CCS)

|
| colspan="2"| 0.54 ± 50%

|
|-
| Bioelectricity with CCS

|
| colspan="2"| 0.30 ± 50%

|
|-
| CH 4 emissions reduction from coal mining

| 0.04

(0.01–0.06)

| 0.41

(0.15–0.64)

| 0.03

(0.02–0.05)

| 0.02

(0.01–0.03)

|
|-
| CH 4 emissions reduction from oil and gas operations

| 0.31

(0.12–0.56)

| 0.61

(0.23–1.30)

| 0.07

(0.03–0.20)

| 0.06

(0.00–0.29)

| 0.10

(0–0.29)

|
|-
| colspan="6"| '''Land-based mitigation options (including agriculture and forestry)'''

| '''Potentials for AFOLU are averages for the period 2020–2050 and represent a proxy for mitigation in 2030.'''

'''Technical potentials listed below include the potentials already listed in the previous columns.'''

'''Note that in Table 7.3 the same potentials are listed, but they are cumulative over the cost bins.'''

|-
| Carbon sequestration in agriculture (soil carbon sequestration, agroforestry and biochar application)

|
| 0.50

(0.38–0.60)

| 0.73

(0.5–1.0)

| 2.21

(0.6–3.9)

|
| Technical potential: 9.5 (range 1.1–25.3).

|-
| CH 4 and N 2 O emissions reduction in agriculture (reduced enteric fermentation, improved manure management, nutrient management, rice cultivation)

|
| 0.35

(0.11–0.84)

| –

| 0.28

(0.19–0.46)

|
| Technical potential: 1.7 (range 0.5–3.2).

GWPs used from AR4 and AR5.

|-
| Protection of natural ecosystems (avoid deforestation, loss and degradation of peatlands, coastal wetlands and grasslands)

|
| 2.28

(1.7–2.9)

| 0.12

(0.06–0.18)

| 1.63

(1.3–4.2)

| 0.22

(0.09–0.45)

| Technical potential 6.2 (range 2.8–14.4).

|-
| Restoration (afforestation, reforestation, peatland restoration, coastal wetland restoration)

|
| 0.15

| 0.57

(0.2–1.5)

| 1.46

(0.6–2.3)

| 0.66

(0.4–1.1)

| Technical potential 5.0 (range 1.1–12.3).

|-
| Improved forest management, fire management

|
| 0.38

(0.32–0.44)

| –

| 0.78

(0.32–1.44)

|
| Technical potential 1.8 (range 1.1–2.8).

|-
| Reduction of food loss and food waste

|
| Feasible potential 0.5 (0.1–0.9).

Technical potential 0.7 (0.1–1.6).

Estimates reflect direct mitigation from diverted agricultural production only, not including land use effects.

|-
| Shift to sustainable healthy diets

|
| Feasible potential 1.7 (1.0–2.7).

Technical potential 3.5 (2.1–5.5).

Estimates reflect direct mitigation from diverted agricultural production only, not including land-use effects.

|-
| '''Buildings'''

|
| '''To avoid double-counting, the numbers were corrected for the potential overlap between options in the order sufficiency, efficiency, renewable measures and they could be therefore added up. In 2050, much larger and cheaper potential is available (see [[IPCC:Wg3:Chapter:Chapter-9#9.6|Section 9.6]] ); the potential in 2030 is lower and more expensive, mostly due to various feasibility constraints.'''

|-
| Sufficiency to avoid demand for energy services (e.g., efficient building use and increased inhabitancy and density)

| 0.56

(0.28–0.84)

|
|-
| Efficient lighting, appliances and equipment, including information and communications technologies, water heating and cooking technologies

| 0.73

(0.54–0.91)

|
|-
| New buildings with very high energy performance (change in construction methods, management and operation of buildings, efficient heating, ventilation and air conditioning)

|
| colspan="3"| 0.35

(0.26–0.53)

| 0.83

(0.62–1.24)

|
|-
| Onsite renewable production and use (often backed-up with demand-side flexibility and digitalisation measures, typically installed in very new high energy performance buildings)

|
| colspan="3"| 0.20

(0.15–0.30)

| 0.27

(0.20–0.40)

|
|-
| Improvement of existing building stock (thermal efficiency of building envelopes, management and operation of buildings, and efficient heating, ventilation and air conditioning leading to ‘deep’ energy savings)

|
| colspan="4"| 0.27

(0.20–0.34)

| Additionally, there is 0.50 (range 0.37–0.62) GtCO 2 -eq of potential above a price of USD200 tCO 2 -eq –1 .

|-
| Enhanced use of wood products

|
| Technical potential 1.0 (range 0.04–3.7).

Economic potential 0.38 (range 0.3–0.5) (varying carbon prices). Potential is mainly in the construction sector.

|-
| '''Transport'''

|
| '''Options for the transportation sector have an uncertainty of ±50%.'''

|-
| Light duty vehicles – fuel efficiency

| 0.6

|
|-
| Light duty vehicles – electric vehicles

|
| Estimated potential is 0.5-0.7 GtCO 2 -eq, depending on the carbon intensity of the electricity supplied to the vehicles. Mitigation costs are variable.

|-
| Light duty vehicles – shift to public transport

| 0.5

|
|-
| Light duty vehicles – shift to bikes and e-bikes

| 0.2

|
|-
| Heavy duty vehicles – fuel efficiency

| 0.4

|
|-
| Heavy duty vehicles – electric vehicles

|
| Estimated potential is 0.2 GtCO 2 -eq. Mitigation costs are variable.

|-
| Heavy duty vehicles – shift to rail

|
| No data available.

|-
| Shipping – efficiency, optimisation, biofuels

| 0.5

(0.4–0.7)

|
|-
| Aviation – energy efficiency

| 0.12–0.32

|
| Limited evidence.

|-
| Biofuels

|
| colspan="3"| 0.6–0.8

|
|-
| '''Industry'''

|
| '''The numbers for the industry sector typically have an uncertainty of ±25%, unless indicated differently.'''

'''The numbers are corrected for overlap between the options, except for the 0.15 GtCO''' 2 '''potential in the highest cost bin. For the rest they can be aggregated to provide full potentials.'''

|-
| Energy efficiency

|
| 1.14

|
| This only applies to more efficient use of fuels. More efficient use of electricity is not included.

|-
| Material efficiency

|
| 0.93

|
|-
| Circularity (enhanced recycling)

|
| 0.48

|
|-
| Fuel switching

|
| 1.28

| 0.67

| 0.15

|
|-
| Feedstock decarbonisation, process change

|
| 0.38

|
|-
| Carbon capture, utilisation and storage (CCU and CCS)

|
| 0.15

(0.08–0.36)

|
|-
| Cementitious material substitution

|
| 0.28

|
|-
| Reduction of non-CO 2 emissions

|
| 0.2

|
|-
| '''Cross-sectorial'''

|
|-
| Emission reduction of fluorinated gases

| 0.26

(0.01–0.50)

| 0.68

(0.55–0.90)

| 0.18

(0.01–0.42)

| 0.09

(0–0.20)

| 0.03

(0–0.05)

| GWPs not updated.

|-
| Reduction of CH 4 emissions from solid waste

| 0.33

(0.24–0.43)

| 0.11

(0.03–0.15)

| 0.06

(0.03–0.08)

| 0.04

(0.01–0.10)

| 0.08

(0.02–0.12)

|
|-
| Reduction of CH 4 emissions from wastewater

| 0.02

(0–0.05)

| 0.03

(0.01–0.05)

| 0.04

(0.01–0.07)

| 0.03

(0.02–0.04)

| 0.07

(0.01–0.16)

|
|-
| Direct air carbon capture and storage (DACCS)

|
| very small

| rowspan="2"| There is potential in these categories, but given the current technology readiness levels, for 2030 the potential is limited. Also, it is not certain whether the costs will have dropped below 200 USD tCO 2 –1 before 2030. In the longer term, much larger potentials are projected, see [[#12.3.1|Section 12.3.1]] .

|-
| Enhanced weathering

|
| very small

|}

Firstly, a brief overview of the process of data collection is presented, with a more detailed overview being found in Supplementary Material 12.SM.1.2. For the energy sector, the starting point for the determination of the emissions reduction potentials was the Emissions Gap Report ( [[#UNEP--2017|UNEP 2017]] ), but new literature was also assessed, and a few studies that provide updated estimates of the mitigation potentials were included. It was found that higher mitigation potentials than in the UNEP report are now reported for solar and wind energy, but at the same time electricity production by solar and wind energy in the reference scenario has increased, compared to earlier versions of the World Energy Outlook. The net effect is a modest increase in the average value of the potential, and a wider uncertainty range. Costs of electricity-generating technologies are discussed in [[IPCC:Wg3:Chapter:Chapter-6#6.4.7|Section 6.4.7]] , with a summary of LCOEs from the literature being presented in [[IPCC:Wg3:Chapter:Chapter-6#6.4.7|Section 6.4.7]] . Mitigation costs of electricity production technology depend on local conditions and on the baseline technology being displaced, and it is difficult to determine the distribution over the cost ranges used in this assessment. However, it is possible to indicate a broad cost range for these technologies. These cost ranges are presented in Table 12.3. For onshore wind and utility-scale solar energy, there is strong evidence that despite regional differences in resource potential and cost, a large part of the mitigation potential can be found in the negative cost category or at cost parity with fossil fuel-based options. This is also the case for nuclear energy in some regions. Other technologies show mostly positive mitigation costs, the highest mitigation costs are for CCS and bioelectricity with CCS, for details see Supplementary Material 12.SM.1.2.

For the AFOLU sector, assessments of global net emissions reduction studies were provided in Table 7.3. The number of studies depends on the type of mitigation action, but ranges from five to nine. Each of these studies relies on a much larger number of underlying data sources. From these studies, emissions reduction ranges and best estimates were derived. The studies presented refer to different years in the period 2020 to 2050, and the mitigation potential presented for AFOLU primarily refers to the average over the period 2020 to 2050. However, because most of the activities involve storage of carbon in stocks that accumulate carbon, or conversely decay over time (e.g., forests, mangroves, peatland soils, agricultural soils, wood products), the 2020 to 2050 average provides a good approximation of the amount of permanent atmospheric CO 2 mitigation that could be available at a given price in 2030. The exception is BECCS, which is in an early upscaling phase, so the potential estimated by [[IPCC:Wg3:Chapter:Chapter-7|Chapter 7]] as an average for the 2020 to 2050 period is not included in Table 12.3. Note that for the energy sector a mitigation potential for BECCS is provided in Table 12.3.

The emissions reduction potentials for the buildings sector were based on the analysis by [[IPCC:Wg3:Chapter:Chapter-9|Chapter 9]] authors of a large number of sectoral studies for individual countries or regions. In total, the chapter analysed the results of 67 studies that assess the potential of technological energy efficiency and onsite renewable energy production and use, and the results of 11 studies that assess the potential of sufficiency measures helping avoid demand for energy and materials. The sufficiency measures were included in models by reorganisation of human activities; efficient design, planning, and use of building space; higher density of building and settlement inhabitancy; redefining and downsizing goods and equipment, limiting their use to health, living, and working standards, and their sharing. Most of these studies targeted 2050 for the decarbonisation of buildings; the potentials in 2030 reported here rely on the estimates for 2030 provided by these studies or on the interpolated estimates targeting these 2050 figures. Based on these individual country studies, regional aggregate emissions reduction percentages were found. The potential estimates were assembled in the order sufficiency, efficiency, renewable options, correcting the amount of the potential at each step for the interaction with preceding measures. Note that the option ‘Enhanced use of wood products’ was analysed by Chapter 7, but is listed under the buildings sector in Table 12.3, as such enhanced use of wood takes place predominantly in the construction sector.

For the transport sector, [[IPCC:Wg3:Chapter:Chapter-10|Chapter 10]] provided data on the emissions reduction potential for shipping. For the other transportation modes, additional sources were used to achieve a complete overview of emissions reduction potentials (for further details, see Supplementary Material 12.SM.1.2). A limited number of estimates for global emissions reduction potential is available: the total number of sources is about 10, and some estimates rely on just one source. The data have been coordinated with [[IPCC:Wg3:Chapter:Chapter-10|Chapter 10]] authors.

For the industrial sector, global emissions reduction potentials per technology class per sector were derived by [[IPCC:Wg3:Chapter:Chapter-11|Chapter 11]] authors, using primarily sectoral or technology-oriented literature. The analysis is based on about 75 studies, including sectoral assessments (Sections 11.4.1 and 11.4.2 and Figure 11.13).

For methane emissions reduction from oil and gas operations, coal mining, waste treatment and wastewater, an analysis was done, based on three major data sources in this area ( [[#Harmsen--2019|Harmsen et al. 2019]] ; [[#US%20EPA--2019|US EPA 2019]] ; [[#Höglund-Isaksson--2020|Höglund-Isaksson et al. 2020]] ); for oil and gas operations this was complemented by [[#IEA--2021a|IEA (2021a)]] . A similar analysis for reductions of emissions of fluorinated gases was carried out based on analysis by the same institutes ( [[#Purohit--2017|Purohit and Höglund-Isaksson 2017]] ; [[#Harmsen--2019|Harmsen et al. 2019]] ; [[#US%20EPA--2019|US EPA 2019]] ). Data for CDR options not discussed previously (such as DACCS and enhanced weathering) were taken from [[#12.3|Section 12.3]] . For more details about data sources and data processing, see Supplementary Material 12.SM.1.2.

In Table 12.4 mitigation potentials for all gases are presented in GtCO 2 -eq. For most sectors the mitigation potentials (notably for methane emissions reductions from coal, oil and gas, waste and wastewater) have been converted to CO 2 -eq using global warming potential (GWP) values as presented in AR6 WGIII (Cross-Chapter Box 2 in Chapter 2). However, the underlying literature did not always accommodate this, in which cases older GWP values apply. Given the uncertainty ranges in the mitigation potentials in Table 12.3, the impact on the results of using different GWP values is considered to be very small.

'''Table 12.4 | Overview of aggregate sectoral net GHG emissions reduction potentials (GtCO''' 2 '''-eq) for the year 2030 at costs below USD100 tCO''' 2 '''-eq''' –1 '''.''' Comparisons with earlier assessments are also provided. Note that sectors are not entirely comparable across the three different estimates.

{| class="wikitable"
|-
! rowspan="2"| '''Sector'''

! colspan="5"| '''Mitigation potentials at costs less than USD100 tCO''' 2 '''-eq''' –1

|-
! AR6

best estimate

! AR6

range

! AR4

( [[#Barker--2007|Barker et al. 2007]] )

! UNEP2017

best estimate

( [[#UNEP--2017|UNEP 2017]] )

! [[#UNEP--2017|UNEP 2017]]

range

( [[#UNEP--2017|UNEP 2017]] )

|-
| Electricity sector

| 11.0

| 7.9–12.5

| rowspan="2"| 6.2–9.3

| 10.3

| 9.5–11.0

|-
| Other energy sector (methane)

| 1.6

| 1.1–2.1

| 2.2

| 1.7–2.6

|-
| Agriculture

| 4.1

| 1.7–6.7

| 2.3–6.4

| 4.8

| 3.6–6.0

|-
| Forestry and other land use-related options

| 7.3

| 3.9–13.1

| 1.3–4.2

| 5.3

| 4.1–6.5

|-
| AFOLU demand-side options (estimates reflect direct mitigation from '''diverted agricultural production only, not including land-use effects)'''

| 2.2

| 1.1–3.6

|
| 1.3–3.4

|-
| Buildings (potentials up to

USD200 '''tCO''' 2 '''-eq''' –1 '''in parentheses)'''

| Dir 0.7

(1.1)

Ind 1.3

(2.1)

Tot 2.0

(3.2)

| 0.5–1.0

(0.7–1.5)

0.9–1.8

(1.5–3.1)

1.4–2.9

(2.3–4.6)

| Dir 2.3–2.9

Ind 3.0–3.8

Tot 5.4–6.7

| Dir 1.9

Ind 4.0

Tot 5.9

| Dir 1.6–2.1

|-
| Transport

| 3.8

| 1.9–5.7

| 1.6–2.5

| 4.7

| 4.1–5.3

|-
| Industry

| Dir 5.4

| 4.0–6.7

| Dir 2.3–4.9

Ind 0.83

Tot 3.1–5.7

| Dir 3.9

Ind 1.9

Tot 5.8

| Dir 3.0–4.8

|-
| Fluorinated gases (all sectors)

| 1.2

| 0.7–1.5

| NE

| 1.5

| 1.2–1.8

|-
| Waste and wastewater

| 0.7

| 0.6–0.8

| 0.4–1.0

| 0.4

| 0.3–0.5

|-
| Enhanced weathering

| –

| –

| –

| 1.0

| 0.7–1.2

|-
| '''Total of all sectors'''

| '''38'''

| '''32–44'''

| '''15.8–31.1'''

| '''38'''

| '''35–41'''

|}

Note: Dir = reduction of direct emissions, Ind = reduction of indirect emissions (related to electricity production), Tot = reduction of total emissions, NE = not estimated, AR4: Table 11.3, UNEP-2017: Chapter 4.

For all options, uncertainty ranges of the mitigation potentials are given in Table 12.3. As far as possible, the ranges represent the variation in assessments found in the literature. This is the case for wind and solar energy, for the AFOLU options, for the methane mitigation options (coal, oil and gas, waste and wastewater) and for fluorinated gas mitigation. For the latter options, some variability exists for each cost bin, but aggregated over cost ranges the variation is much smaller, typically ±50%. For the buildings sector and the industrial sector options, the uncertainty in the mitigation potential is estimated by the lead authors of those chapters. For options for which only limited sources were available, an uncertainty range of ±50% was used. Overall, the uncertainty range per option is typically in the range of ±20% to ±60%.

Despite these uncertainties, clearly a number of options with high potentials can be identified, including solar energy, wind energy, reducing conversion of forests and other natural ecosystems, and restoration of forests and other natural ecosystems. As mid-range values, they each represent 4 to 7% of total reference emissions for 2030. Soil carbon sequestration in agriculture and fuel switching in industry can also be considered as options with high potential, although it should be noted that these options consist of a number of discernible sub-options, see Table 12.3. It can be observed that for each sector, a variety of options is available. Many of the smaller options each make up 1 to 2% of the reference emissions for 2030. Within this group of smaller options there are some categories that, summed together, stand out as substantial: the energy efficiency options and the methane mitigations options.

Costs are highly variable across the options. All sectors have several options for which at least part of the potential has mitigation costs below USD20 tCO 2 –1 . The only exception is the industrial sector, in which only energy efficiency is available below this cost level. At the same time, a substantial part of the emissions reduction potential comes at higher cost, much being in the USD20 to 100 tCO 2 –1 cost ranges. All sectors have substantial additional potential in these cost ranges; only for transportation is this limited. Aggregation of the potentials per cost bin shows that the potential in these cost bins is marginally smaller than in the two cheapest cost bins. For some options, potential was identified in the 100 to 200 tCO 2 –1 cost bin. The mitigation potentials identified in this cost range make up only a small part of the total mitigation potential. It could be that there is limited potential in this range; however, a more plausible explanation, supported by several authors of sectoral chapters, is that this cost range is relatively unexplored.

In this assessment, the emphasis is on the specific mitigation costs of the various options, and these are often considered as an indicator to prioritise options. However, in such a prioritisation, other elements will also play a role, like the development of technology for the longer term ( [[#12.2.4|Section 12.2.4]] ) and the need to optimise investments over longer time periods, see for example [[#Vogt-Schilb--2018|Vogt-Schilb et al. (2018)]] who argue that sometimes it makes sense to start with implementing the most expensive option.

In this section, an overview of emissions mitigation options for the year 2030 was presented. The overview of the mitigation potential is based on a variety of approaches, relying on a large number of sources, and the number of sources varied strongly from sector to sector. The main conclusions from this section are: (i) there is a variety of options per sector, (ii) per sector the options combined show significant mitigation potential, (iii) there are a few major options and a lot of smaller ones, and (iv) more than half of the potential comes at costs below USD20 tCO 2 –1 (between sectors: ''medium'' to ''robust evidence'' , ''h'' ''igh agreement'' ).

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