A fuel made by fermenting sugars from corn or sugarcane is called what?

A facility uses transesterification to convert soybean oil into a transportation fuel. What fuel does it produce?

A dairy farm burns the fuel produced by an oxygen-free manure digester to heat its barns. What biomass fuel is the farm using?

A sawmill compresses dry sawdust into dense cylinders for home heating. What biomass fuel has it made?

A plant breaks down the fibrous stalks of switchgrass into sugars and ferments them into a liquid transportation fuel. Which fuel pathway is this?

A landfill collects methane formed as waste decomposes and upgrades it for vehicle use. What renewable fuel results?

When comparing a biofuel with gasoline, which measure best evaluates the biofuel's climate impact?

A biofuel pathway emits 58 g CO₂e/MJ across its lifecycle, while gasoline emits 94 g CO₂e/MJ. A report lists the biofuel as zero by counting only crop uptake. What value describes the pathway?

Wood pellets are burned now, while replacement trees will take decades to grow. Which statement best evaluates a claim that the pellets are automatically carbon-neutral?

A fuel pathway releases 14 g CO₂e/MJ growing feedstock, 20 processing it, 5 transporting it, and 55 burning it. Crop growth removes 70 g CO₂e/MJ. What is its net lifecycle emission?

An ethanol plant currently burns natural gas for distillation. Which change would directly lower the fossil-energy portion of its lifecycle emissions?

A student says, “A biofuel vehicle emits no carbon dioxide because its feedstock was a crop.” What is the best correction?

A company clears a forest to plant sugarcane for ethanol. Why can a tailpipe-only estimate understate the fuel's climate impact?

A biofuel yields 12 MJ of usable energy for every 3 MJ invested in growing, processing, and transport. What is its energy return on investment?

Fuel A returns 1.25 units of energy per unit invested, and Fuel B returns 5. A refinery needs 100 units of usable energy. Which fuel requires more energy input, and by how much?

A biodiesel pathway requires 50 MJ of energy inputs and provides 65 MJ of usable fuel energy. What is its net energy?

Use the table to find the net energy of this biofuel pathway.

Process A delivers 120 MJ of useful fuel from 40 MJ invested. Process B delivers 90 MJ from 45 MJ invested. What is the energy return on investment of the process with the higher return?

An ethanol plant uses waste heat from its electricity generator to dry its distillers grains instead of burning extra fuel. What is the likely effect on net energy?

When a large share of a corn crop is diverted from food and livestock feed to ethanol, what trade-off does this create?

A producer replaces corn grown on prime cropland with switchgrass grown on marginal land. Which direct land-use trade-off is most reduced?

Soybean biodiesel demand leads growers to clear a forest for new fields. What land cost is most directly associated with that expansion?

A farmer removes nearly all corn stover from a field each year for cellulosic ethanol. What concern should be evaluated at the field?

An algae-biofuel facility is built on nonarable land rather than on cropland. Which land-use conflict is it designed to reduce?

A county converts 1,000 hectares of cattle pasture to an energy-crop plantation. What is the immediate opportunity cost of this land decision?