# Presentation: 591141

## Margaret K. Mann

**Margaret K. Mann**
**National Renewable Energy Laboratory**
**Golden, Colorado  USA**

## Short discussion of life cycle assessment (LCA)

Purpose of LCAs conducted

System descriptions
Biomass IGCC
Average coal
Coal/biomass cofiring
Natural gas combined cycle

Comparative Results
Energy
Greenhouse gases
Other air emissions
Resource consumption

- Purpose of LCAs conducted
- System descriptions
- Biomass IGCC
- Average coal
- Coal/biomass cofiring
- Natural gas combined cycle
- Comparative Results
- Energy
- Greenhouse gases
- Other air emissions
- Resource consumption

**Outline of Presentation**

## LCA is:
a systematic analytical method
used to quantify the environmental benefits and drawbacks of a process
performed on all processes, cradle-to-grave, resource extraction to final disposal
ideal for comparing new technologies to the status quo
helps to pinpoint areas that deserve special attention
reveals unexpected environmental impacts                                   (no show-stopping surprises)

**Life Cycle Assessment: Definition**

- LCA is:
- a systematic analytical method
- used to quantify the environmental benefits and drawbacks of a process
- performed on all processes, cradle-to-grave, resource extraction to final disposal
- ideal for comparing new technologies to the status quo
- helps to pinpoint areas that deserve special attention
- reveals unexpected environmental impacts                                   (no show-stopping surprises)

## System Concept in Life Cycle Assessment

**System Concept in Life Cycle Assessment**

- Life cycle system boundary

## Three Components of LCA

**Three Components of LCA**

**INVENTORY**
- Mass and energy balances >> air, water, and solid waste emissions, energy and resource consumption
**IMPROVEMENT**
- Reduce environmental burden through process design changes, material substitution, recycle, etc.
**IMPACT ASSESSMENT**
- Characterize environmental effects
- Less-is-better
- Stressor categories: climate change gases, carcinogens, resource depletion, ozone precursors
- Weighting factors: e.g., methane = 21 * CO2
- Valuation: Assign values to each effect to achieve an overall environmental score or set of scores

## Biomass LCA was conducted to answer common questions:
What are the net CO2 emissions?
What is the net energy production?
Which substances are emitted at the highest rate?
What parts of the system are responsible for the greatest impacts?
What should biomass R&D focus on?

Coal and natural gas LCAs the foundation for quantifying the benefits of biomass power.

Direct-fired biomass system describes current biomass power industry.

Cofiring LCA examined near-term option for biomass utilization.

Each assessment conducted separately - common systems not excluded.

**Purpose of Studies**

- Biomass LCA was conducted to answer common questions:
- What are the net CO2 emissions?
- What is the net energy production?
- Which substances are emitted at the highest rate?
- What parts of the system are responsible for the greatest impacts?
- What should biomass R&D focus on?
- Coal and natural gas LCAs the foundation for quantifying the benefits of biomass power.
- Direct-fired biomass system describes current biomass power industry.
- Cofiring LCA examined near-term option for biomass utilization.
- Each assessment conducted separately - common systems not excluded.

## Systems Examined

**Systems Examined**

- Indirectly-heated gasification

- Dedicated hybrid poplar feedstock

- Zero carbon sequestration in base case

- Pulverized coal / steam cycle

- Illinois #6 coal - moderate sulfur, bituminous

- Surface mining

- Biomass IGCC

- Average coal

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## Example flows:
Biomass energy crop - photosynthesis, carbon sequestration in soil
Biomass residue - avoided decomposition emissions
Coal - coal mine methane, coal mine waste
Natural gas- fugitive emissions, leaks
General - incomplete combustion, upstream fossil fuel consumption

**Carbon Cycle (GHG Emissions)**

- Example flows:
- Biomass energy crop - photosynthesis, carbon sequestration in soil
- Biomass residue - avoided decomposition emissions
- Coal - coal mine methane, coal mine waste
- Natural gas- fugitive emissions, leaks
- General - incomplete combustion, upstream fossil fuel consumption

- Key question: On a life cycle basis, what are the net greenhouse gas emissions of these systems?

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## -41 g/kWh

- -15

- -5

- 5

- 15

- Particulates

- SOx

- NOx

- CO

- NMHCs

- Average PC coal

- 15% Coal / biomass cofiring

- Direct biomass residue

- Dedicated biomass IGCC

- NGCC

- CH4

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- Coal

- Limestone

- Oil

- Natural Gas

- Average PC coal

- 15% cofiring

- Direct-fired residue biomass

- Dedicated biomass IGCC

- NGCC

## Summary

**Summary**

**Greenhouse Gases:**
- Biomass IGCC nearly zero net GHGs
- Average coal system: ~1,000 g CO2-equiv/kWh
- NGCC system: ~500 g CO2-equiv/kWh
- Today’s biomass systems remove GHGs from atmosphere
**Energy:**
- Coal and natural gas: negative system energy balance
- Even neglecting the energy content of coal and natural gas, biomass systems are more energy efficient
- NGCC: natural gas extraction and losses account for 21% of total energy
**Air emissions:**
- Biomass: few particulates, SO2, NOx, and methane
- Coal: upstream CO and NMHC emissions lower
- NGCC: system methane emissions high
**Resource consumption:** Biomass systems << fossil systems
**Cofiring:**
- 15% cofiring reduces GWP of coal system by 18%
- Reduction in emissions, resource consumption, and energy use