Integrated Assessment Modeling of Land-Use Implications of Bioenergy

Transcription

1 Integrated Assessment Modeling of Land-Use Implications of Bioenergy KATE CALVIN, LEON CLARKE, JAE EDMONDS, MARSHALL WISE February 26, 2018 PNNL-SA

2 Limiting Global Mean Temperature to 2 C or below requires substantial emissions reductions. Absent any climate mitigation, radiative forcing and temperature are expected to rise. The non-mitigation cases in the IPCC AR5 had 2100 radiative forcing between 6 and 9 W/m 2. In contrast, the 2 C scenarios have radiative forcing at ~2.6 W/m 2. Total Radiative Forcing, in baseline simulations (black) and the RCPs (colors) Source: Clarke et al. (2014) February 26,

3 Limiting Global Mean Temperature to 2 C or below requires substantial emissions reductions. The IPCC AR5 WG3 estimates that cumulative carbon emissions need to be limited to GtCO 2 in order to keep temperature to 2 C. However, this depends on: How the temperature target is defined, Climate sensitivity and other uncertainties in the climate system, The level of non-co 2 emissions, both baseline levels and mitigation potential. CO 2 Emissions in 2C Budgets, with (green) and without (blue) negative emissions Source: van Vuuren et al. (2017) February 26,

4 Different IAMs take different approaches to how they find 2 C scenarios. Climate: Some IAMs have a climate model and can compute temperature change for each emissions scenario calculated. Others use an emissions budget. Cumulative BECCS in 2 C Scenarios Land: Some models have an explicit land model that computes bioenergy supply and land use emissions. Some models use bioenergy supply curves and either (1) assume no land use emissions or (2) use a look up table. Source: Fuss et al. (2016) February 26,

5 The Global Change Assessment Model (GCAM) 32 Energy/Economy Regions ~300 Agriculture/Land Use Regions GCAM is a global integrated assessment model GCAM links Economy, Energy, Land, and Climate systems Typically used to examine the effect of technology and policy on the economy, energy system, agriculture and land-use, and climate. Technology-rich model. Emissions of 24 greenhouse gases and short-lived species. Captures linkages between regions through trade in energy & agricultural goods. Runs through 2100 in 5-year time-steps. Open source: Documentation available at: Note: All results in this presentation use GCAM4.4, the current public release version.

6 GCAM calculates temperature using a climate emulator, and can solve for 2 C. In GCAM, we use a carbon price to reduce emissions and adjust that price until the 2 C target is met. Such a procedure gives both a total carbon budget and the time pathway for reducing emissions. The specific budget will vary based on other scenario characteristics that dictate both baseline non-co 2 emissions and non-co 2 mitigation potential. The time path is chosen to minimize the cost of mitigation. Global CO 2 Emissions in GCAM4.4, with (purple) and without (green) afforestation February 26,

7 The GCAM Energy System Demand: We calculate energy service demand as a function of income and energy cost. Technology choice to meet those service demands depends on cost. Supply: We use graded depletable (fossil fuels, uranium) and renewable (solar, wind) resource curves to represent supply. The choice of technology (and fuel) to meet in the transformation sectors (e.g., electricity, refined liquids) depends on cost. Note: GCAM uses a logit formulation and not a winner-take-all approach. As a result, we get a distribution of energy technologies in each time period. 7

8 IAMs reduce emissions by adjusting the energy and land systems. In GCAM, the imposition of a carbon price alters the cost of energy technologies, incentivizing low carbon fuels. The result is a change in the fuel mix favoring low carbon technologies, and A change in overall energy demand, either via energy efficiency gains or reductions in energy services. Levelized Cost of Electricity Generation in 2100 in a 2 C Scenario Note: Only includes a subset of GCAM technologies. February 26,

9 The GCAM Land System Demand: We calculate demand for food, feed, and fuel as a function of income and price. Supply: Supply depends on land allocation and the (exogenous) yield. Land Allocation: Land owners allocate land across a variety of uses in order to maximize profit. There is a distribution of profits for each land type in each region. The actual share of land allocated to a particular use is the probability that land type has the highest profit. February 26,

10 IAMs reduce emissions by adjusting the energy and land systems. In GCAM, the imposition of a carbon price alters the profit rate of different land types. Profit rates are sensitive to the land policy context (e.g., afforestation incentives). Bioenergy profit depends on the price of bioenergy, which can increase substantially in mitigation cases. Food demand is very inelastic, so food prices will rise in mitigation cases to ensure enough land is allocated for food production. Profit Rate by Land Type in USA AEZ08 in 2100 in the 2 C, with (bottom) and without (top) afforestation Note: Only includes a subset of GCAM land types. 10

11 Limiting GMT to 2 C in GCAM results in substantial reductions in emissions and increases in carbon price. Global CO 2 Emissions in GCAM4.4, with (purple) and without (green) afforestation CO 2 Price in GCAM4.4, with (purple) and without (green) afforestation February 26,

12 These changes in carbon price incentivize low carbon technologies, like BECCS. Bioenergy Price, with (purple) and without (green) afforestation Total Bioenergy Consumption, with (purple) and without (green) afforestation February 26,

13 These changes in carbon price incentivize afforestation (when available). Changes in bioenergy price incentivize bioenergy land. Global Land Cover in GCAM4.4, with (right) and without (left) afforestation February 26,

14 Limiting GMT to 2 C in GCAM. GCAM calculates the pathway to 2 C by minimizing mitigation cost subject to the assumptions, constraints, and policies imposed. A 2 C world is fundamentally different than today with different economic incentives leading to very different energy and land systems. Like other IAMs, we get a fair amount of BECCS because of (1) the emissions constraint imposed, (2) the cost of BECCS relative to other low carbon technologies, and (3) the limited CDR options available. BECCS accounts for 27% of the global energy use in Excluding BECCS results in earlier emissions reductions and can result in more bioenergy used. Including other CDR options (like afforestation) may reduce BECCS use. The technology and policy context matters in determining BECCS and afforestation use. February 26,

15 Research Needs for IAMs and CDR For the IAM community: Incorporation of other CDR options (e.g., direct air capture, soil carbon sequestration). Explicitly representing other factors that may affect bioenergy deployment (e.g., water). More sensitivity/uncertainty analyses exploring the implications of various parameters and assumptions. Better communication of results. For the broader community: Better estimates of critical parameters (e.g., bioenergy yield, technology cost, groundwater availability). Finer scale modeling to explore feasibility and implications of the changes. Cooperation among research communities (e.g., agronomists, policy experts, etc.). February 26,

16 Thank you! February 26,