Bioenergy and Waste-to-Energy Flashcards

Which feedstock characteristic is expressed by the 'C:N ratio' and is critical for optimizing anaerobic digestion performance?

Answer: Carbon-to-nitrogen ratio, which ideally should be 20:1 to 30:1 for stable digestion

The carbon-to-nitrogen ratio of 20:1–30:1 balances microbial carbon needs with nitrogen requirements, preventing ammonia inhibition or carbon limitation.

Which policy mechanism under the 2022 Inflation Reduction Act specifically expanded incentives for biogas and biomethane projects in the U.S.?

Answer: Section 45Z Clean Fuel Production Credit covering biomethane sold as transportation fuel

The Section 45Z Clean Fuel Production Credit (effective 2025) supports biomethane and other low-carbon fuels based on lifecycle emissions intensity.

What is the main technical challenge of using biomass with high alkali and chlorine content (such as agricultural straws) in direct combustion boilers?

Answer: Ash slagging, fouling, and high-temperature corrosion of heat exchange surfaces

Alkali metals (potassium, sodium) and chlorine in straw biomass form low-melting compounds that cause deposit buildup and corrosion on boiler tubes.

In the context of bioenergy with carbon capture and storage (BECCS), what makes it a potential 'negative emissions' technology?

Answer: Biogenic CO2 absorbed during plant growth is permanently stored underground after capture

BECCS removes atmospheric CO2 through biomass growth and permanently sequesters the biogenic CO2 captured during combustion or conversion underground.

Which biological pretreatment method can break down lignocellulosic biomass without chemicals or high temperatures, making cellulose more accessible for fermentation?

Answer: White-rot fungal (fungal) pretreatment using ligninolytic enzymes

White-rot fungi secrete ligninolytic enzymes (laccases, peroxidases) that selectively degrade lignin, exposing cellulose and hemicellulose without chemical inputs.

A biorefinery concept that maximizes value from biomass by producing both biofuels and high-value co-products is analogous to which existing industry?

Answer: A petroleum refinery producing fuels, chemicals, and materials from crude oil

Like petroleum refineries that extract multiple product streams from crude oil, biorefineries fractionate biomass into fuels, chemicals, materials, and energy to maximize economic value.

Which federal program requires large food waste generators in certain jurisdictions to divert organic waste from landfills, indirectly supporting biogas production?

Answer: State-level organics recycling mandates (e.g., California AB 1826) enabled by EPA Food Recovery Hierarchy goals

State organics diversion mandates like California AB 1826, aligned with EPA's Food Recovery Hierarchy, require large generators to source-separate organics, feeding AD and composting facilities.