Biomass (liquid)

Summary

Current and future “renewable” fuel

  • Pure ethanol (E100 → Brazil’s “alchohol”)

  • Ethanol at E85 (85% ethanol)

  • Ethanol in gasoline (~10%; E10)

  • Biodiesel

Ethanol and Biodiesel

  • USA → E85 (85% ethanol, 15% gasoline) + gasoline (~10% ethanol) from maize (corn)

  • Brazil → 100% ethanol (“alcohol”) + gasohol (~25% ethanol), from sugarcane

  • Brazil, USA → “flex” engines burn ethanol- gasoline blends

  • Biofuels (ethanol in gasoline; biodiesel in diesel), ~2% US total energy consumption

US energy consumption

Biofuels, 6% of transport is powered by renewable energy.

Renewable Energy in US: increase in 1970s (ethanol boom)… stagnant until early 2000s… rapid increase to 2012 (ethanol statutes), then stagnant

Primary Production

Production (mass/area):

  • Photosynthesis: electromagnetic energy converted to chemical energy (carbohydrate)

  • Geographical variation… ecosystem-based variation… depending on solar radiation, precipitation, etc.

Limits to biomass production:

  • theoretical total…. harvestable total… 1.5 × 10^19 J is <10% of total current energy use.

  • But… energy is used to cultivate, harvest, process, and distribute biomass… and energy content varies among plant components.

Energy (solar; fossil fuel) → Grow feedstocks (soy; sugarcane) → use energy to convert feedstock to ethanol or biodiesel

Leading-Edge Biomass

  • Algae, inedible cover crops, bagasse, etc.

  • Use of wastewater to grow algae → biorefineries co-located with hydrocarbon refineries → “sustainable aviation fuel”

  • Use of cellulosic plants (switchgrass, bagasse from sugarcane or sweet sorghum) →

Value chain:

firms, organizations in network; influence government through lobbying → subsidies, grants, trade protection

Key Policies:

Energy Tax Act 1978 → High oil prices encourage ethanol as a potential substitute for foreign oil; lobbying groups successful; R&D for ethanol-supported

Clean Air Act, 1992: ethanol as additive (MTEB) to encourage lower vehicle emissions

Biomass Research and Development Act 2000: encourage R&D through low-interest loans; further evidence for lobbying group strength

Energy Policy Act, 2005: 25% of US energy sourced from renewables by 2025; strong support in Iowa

Energy Independence and Security Act, 2007- Renewable Fuel Standard (2005,2007): Large ethanol mandate through blend requirement. Reduce lifecycle GHG by 20% compared to gasoline

The land Question: how much energy from land area (hectare)?

Ethanol:

  • Sugarcane → 6,000 I/ha, or 140 GJ/ha

  • Maize → 3,000 I/ha, or 80 GJ/ha (or animal feed? or food?)

Biodiesel:

  • Soybean → 900 i/ha, or 140 GJ/ha

  • Oil palm → 4,500 I/ha, or 150 GJ/ha

“Renewable” Future?

Criticisms of biofuels:

  • Expensive and ineffective at lowering petroleum consumption for transport: esp. maize

Maize:

  • all US maize diverted to ethanol would replace 12% of gasoline demand… with many side effects

  • poor energy ratio (approx 1.25-1.35)

Smil (1983: 295): “ethanol from farm crops is an idea whose time should not come

  • one poor person: rely on 0.1 ha for 200 kg grain/yr

  • One affluent meat-eater: rely on 0.3 ha for 700 kg grain/yr

  • One gasoline car (16K k/yr): relies on 3 ha for 6,000 kg grain

Unnecessary intensification of farming

  • More mechanization, more fertilizers → more fossil fuels, more nitrogen runoff, less land for conservation

  • Carbon “debt”: how much time is required for biofuel “savings” to offset carbon emissions from clearing land for planting biofuels?

  • “Hidden” environmental impact: new lands cleared → “Switch to corn promotes Amazon deforestation”

“Green” cloak of farm subsidies:

  • US direct corn subsidies: $8.9B in 2005

  • US protection against imported ethanol

Increase cost of food:

  • Biofuel “could starve the poor”:: corn for ethanol → lower stocks → higher prices for corn

  • Biofuel as “crime against humanity”

Environmental outcomes of the US Renewable Fuel Standard

Renewable Fuel Standard defined in 2005, 2007 → insert corn ethanol into gasoline

Impacts:

  • increased corn prices by 30% and the prices of other crops by 20% → expanded US corn cultivation 8.7%

  • Increased annual nationwide fertilizer use by 3 to 8%

  • Increased water quality degredants by 3 to 5%

  • Caused enough domestic land use change emissions such that the carbon intensity of corn ethanol produces under the RFS is no less than gasoline and likely at least 24% higher.