This article explains the dynamics of bioenergy in En-ROADS. Watch the video below for a summary.

Bioenergy is energy produced by the burning of biomass—biological material including trees, agricultural crops, waste, or other sources such as algae. These raw materials, known as feedstocks, are modeled individually in En-ROADS. The main focus here is on wood bioenergy because it is a source of forestry and land use emissions.

To see the effect of bioenergy on carbon emissions and removals, subsidize bioenergy.

Subsidizing bioenergy has three significant effects in En-ROADS: it increases CO2 emissions, reduces the removal of CO2 from the atmosphere, and competes with other sources of energy.

1. More CO2 emissions, due to burning wood and the release of carbon from the soil
Cutting down trees and burning wood for bioenergy releases stored carbon from forests and soil into the atmosphere in the form of CO2. These emissions are shown in the “CO2 Gross Emissions from Forest Bioenergy” graph (under Graphs > CO2 Emissions). Carbon from trees is released immediately when wood is burned, whereas carbon in the soil is released over several decades after the soil has been disturbed by tree harvesting. The bioenergy subsidy causes the blue line of the Current Scenario to depart from the black line of the Baseline Scenario:

2. Less CO2 removal, due to forest degradation
Harvesting forests for bioenergy reduces the ability of the land to remove carbon from the atmosphere long after harvest. Forests remove CO2 from the atmosphere via photosynthesis, sequestering the carbon in plants and soils. Harvesting forests for energy results in forest degradation, and it prevents growth and CO2 removals that would have occurred if the forest were not harvested. When trees are cut down for bioenergy, new trees grow, but it takes several decades for the young trees to remove as much CO2 as the older trees they replaced. 

The “CO2 Removals from Land” graph (under Graphs > CO2 Removals) shows that with increased bioenergy harvesting as a result of the bioenergy subsidy, CO2 removals go below the Baseline and take several decades to return to what they would have been. The change is small because the increase in bioenergy harvesting is only so big relative to total CO2 removals from land.

The “CO2 Net Emissions from Forest Bioenergy” graph under Graphs > CO2 Emissions combines both the gross emissions and the change in CO2 removal capacity.

En-ROADS assumes that forested land that is harvested for bioenergy is regrown and remains forested, rather than being converted to farmland, urban areas, or other types of land. In the real world, however, regrowth is not guaranteed. Young trees are more susceptible to fire, insects, and damage from extreme weather, and land may be used for other purposes such as agriculture in the future.

Read more about the forest dynamics in the Explainer on Land and Forests in En-ROADS.

3. Competition with other energy sources

Bioenergy competes with fossil fuels (coal, oil, and natural gas) and renewable energy. A bioenergy subsidy will cause bioenergy to replace some fossil fuels, slightly reducing the CO2 emissions from fossil fuels but also reducing renewable energy’s contribution to the energy system:

Overall result of an increase in bioenergy:

Combining these three factors above results in higher CO2 net emissions overall, seen in the “CO2 Net Emissions” graph under Graphs > CO2 Emissions:

The net effect is that carbon is moved from soils and biomass into the atmosphere. The “Carbon in Forests–Area” graph (left) shows the decline of carbon in soils and plants relative to the Baseline Scenario (black line). This results in the amount of carbon in the atmosphere increasing, shown in the “CO2 Concentration” graph (right).

Adjusting the bioenergy feedstocks individually

En-ROADS models three categories of material used for bioenergy production, referred to as “feedstocks”:

  • Wood (e.g., wood pellets and firewood)
  • Crops (e.g., maize and soybean oil to make ethanol and biodiesel)
  • Waste/other (e.g., methane from decomposition in landfills)

The main Bioenergy slider in En-ROADS models a tax or subsidy on all these feedstocks. Setting the main Bioenergy slider to -$25/boe will subsidize all three feedstocks by -$25/boe each. Alternatively, the three feedstocks can be individually taxed or subsidized by selecting “Use detailed settings” under the Bioenergy slider advanced settings:

The following sections provide more detailed context.

Context and background

Wood bioenergy results in significant CO2 emissions, as our team has previously published in in-depth research. Despite this, many governments, including the United States and the European Union, classify bioenergy as a carbon-neutral source of energy, regardless of feedstock, which is incentivizing the growth of bioenergy industries such as wood pellet production.

Crop, waste, and other non-wood feedstocks are considered carbon neutral in En-ROADS. Crops are rapidly regrown, so the CO2 that is released and removed occurs within a year. Waste and other types of feedstocks can result in sources of CO2 emissions, but the relative contribution of those emissions is small globally so they are not yet accounted for individually in the bioenergy carbon dynamics of En-ROADS.

Bioenergy faces supply limitations

A bioenergy subsidy causes a cycle of rising and falling bioenergy use, a classic cycle that occurs when resources face supply limitations. A subsidy makes bioenergy less expensive, so demand increases. More demand for bioenergy causes the feedstock supply to fall—trees in easily accessible areas are cut down and take time to regrow. Alternative sources of trees are more expensive (e.g., additional costs of land acquisition, securing the necessary rights, and longer supply chains). As a result, prices increase, causing demand to go down. In a scenario with a -$25/boe bioenergy subsidy, demand falls after 2060, shown in the “Bioenergy Primary Energy Demand” graph below. With lower demand, trees have time to regrow, and the supply increases again. The price goes down, demand goes up, and the cycle repeats.

How to model less bioenergy

To explore a scenario with less bioenergy, there are several options in En-ROADS:

  1. Tax bioenergy using the Bioenergy slider.
  2. Restrict the harvesting of wood from older forests for bioenergy. In the Deforestation advanced settings, the slider “Reduction in mature forest degradation” simulates a reduction in harvesting forests over 100 years old.
  3. Simulate societal pressure against investment in new bioenergy infrastructure. The slider “Reduce new bioenergy infrastructure” covers factors such as stricter government regulations, policies that phase out bioenergy, or corporate commitments not to use bioenergy. The “Year to reduce new bioenergy infrastructure” slider below it adjusts the start year for this resistance.

Carbon price and bioenergy

A carbon price makes energy sources more expensive depending on how much CO2 they release. Although bioenergy releases CO2, by default in En-ROADS the Carbon Price slider does not apply a carbon price to bioenergy.

Most carbon prices currently enacted around the world do not tax bioenergy—for example, the EU’s emissions trading system considers bioenergy power plant emissions to be zero. Therefore, raising the carbon price in En-ROADS incentivizes bioenergy because its fossil fuel competitors (coal, oil, and natural gas) get more expensive.

The “Carbon price applies to bioenergy emissions” switch in the Carbon Price slider’s advanced settings causes a carbon price to also apply to bioenergy:

Bioenergy with carbon capture and storage (BECCS)

Bioenergy with carbon capture and storage (BECCS) is an experimental method of energy generation and technological carbon dioxide removal. BECCS entails burning biomass for energy, capturing the CO2 emissions, storing the emissions long-term, and successfully re-growing any used biomass to result in a process that stores more carbon than it releases. BECCS relies on the success of emerging technologies and availability of sustainable sources of biomass.

A small amount of BECCS is present in the Baseline Scenario in En-ROADS. To increase the amount of BECCS in a scenario, add a carbon price.