LCA for Chemicals and Materials

The chemical industry produces the building blocks for nearly every manufactured product—plastics, solvents, pharmaceuticals, fertilizers, and countless specialty materials. Life Cycle Assessment in this sector addresses complex supply chains, allocation challenges from multi-output processes, and the growing imperative to transition toward sustainable feedstocks.

Why LCA for Chemicals?

Foundational industry: Chemicals are inputs to virtually every other sector. Upstream impacts cascade through supply chains.

Decarbonization pressure: The chemical industry accounts for significant global CO₂ emissions; pathways to net-zero require life cycle evaluation.

Feedstock transition: Bio-based and recycled feedstocks are emerging; LCA is essential for credible sustainability claims.

Allocation complexity: Chemical plants produce multiple outputs; allocation methods significantly affect results.

Regulatory relevance: REACH, PEF, and other regulations increasingly require life cycle information.

Methodological Considerations

Unique Challenges

Multi-output processes: Refineries and crackers produce dozens of co-products simultaneously. Allocation choices dramatically affect individual product footprints.

Complex supply chains: A single polymer may involve petroleum extraction, refining, cracking, polymerization, and compounding—each with its own allocation challenges.

Recycled content claims: The "mass balance approach" for chain of custody creates unique methodological considerations (see Track 1, Lesson 7).

Process variations: The same chemical can be produced through multiple routes with very different impacts.

Functional Unit

Chemical LCAs typically use mass-based functional units:

• "1 kg of polyethylene resin, at factory gate"
• "1 kg of ammonia (NH₃), industrial grade"
• "1 tonne of sulfuric acid, 98% concentration"

For downstream applications, function-based units are preferred:

• "Coating protection for 1 m² for 10 years"
• "Adhesion bonding 100 joints to specified strength"

Allocation Approaches

The chemical industry presents classic allocation challenges:

Petroleum refining: Produces gasoline, diesel, jet fuel, naphtha, residual oil simultaneously

Steam cracking: Produces ethylene, propylene, butadiene, aromatics, and fuel gases

Chlor-alkali process: Produces chlorine and sodium hydroxide in fixed ratio

Allocation options:

Major Chemical Categories

Basic Petrochemicals

Olefins (ethylene, propylene)

• Primary building blocks for polymers
• Produced via steam cracking of naphtha or ethane
• GWP: ~1.5-2.5 kg CO₂e/kg (varies by feedstock and allocation)

Aromatics (benzene, toluene, xylene)

• Derived from reforming or cracking
• Used in plastics, fibers, solvents
• GWP: ~1.0-2.0 kg CO₂e/kg

Synthesis gas route

• Ammonia, methanol, hydrogen
• Energy-intensive processes
• Ammonia GWP: ~2-3 kg CO₂e/kg (conventional)

Polymers

Polyethylene (PE)

• Highest volume plastic
• HDPE, LDPE, LLDPE variants
• GWP: ~1.8-2.5 kg CO₂e/kg

Polypropylene (PP)

• Versatile thermoplastic
• GWP: ~1.5-2.2 kg CO₂e/kg

PET (Polyethylene terephthalate)

• Beverage bottles, fibers
• GWP: ~2.5-3.5 kg CO₂e/kg

PVC (Polyvinyl chloride)

• Construction applications
• Chlorine production is energy-intensive
• GWP: ~2.0-3.0 kg CO₂e/kg

Specialty Chemicals

Higher value, lower volume, often more complex LCAs:

• Surfactants: Cleaning products, personal care
• Adhesives and sealants: Multiple chemistries
• Coatings: Paints, industrial coatings
• Catalysts: Enable efficient production

Specialty chemicals often have less available LCI data than basic chemicals.

Sustainable Feedstock Transitions

Bio-based Chemicals

Potential benefits:

• Renewable carbon source
• Potential GHG benefits (depends on feedstock and land use)
• Reduced fossil resource depletion

LCA considerations:

• Land use and land use change impacts
• Agricultural inputs (fertilizers, pesticides)
• Competition with food production
• Processing efficiency vs. petrochemicals

Examples:

• Bio-ethylene (from bio-ethanol)
• PLA (polylactic acid from corn starch)
• Bio-PE, Bio-PET (drop-in replacements)

Recycled Feedstocks

Mechanical recycling:

• Physical reprocessing of plastic waste
• Quality degradation limits applications
• Lower GWP than virgin (typically 30-70% reduction)

Chemical/advanced recycling:

• Breaks polymers back to monomers or feedstocks
• Higher energy input but can handle mixed/contaminated waste
• Mass balance approach for content claims

Carbon Capture and Utilization (CCU)

Using captured CO₂ as feedstock:

• CO₂-to-methanol: Combines captured CO₂ with hydrogen
• CO₂-to-polymers: Direct incorporation into certain polymers

LCA considerations:

• Carbon source (fossil point source vs. direct air capture)
• Energy source for conversion
• Product lifetime and fate (temporary vs. permanent storage)
• System boundary choices affect conclusions dramatically

Case Study: Polymer Comparison

Scenario

Comparing 1 kg of polymer for flexible packaging:

• Conventional LDPE
• Bio-based PE (from sugarcane ethanol)
• Recycled PE (mechanical recycling)

Results Summary

*Bio-PE range depends heavily on land use change assumptions

Key Trade-offs

Bio-PE:

• Lower fossil resource use
• GWP benefit depends on land use change accounting
• Higher land and water use
• Agricultural supply chain variability

Recycled PE:

• Clear GWP benefit
• Limited by collection and quality
• Lower performance may require virgin blending
• Supports circular economy

Data Sources

Industry Programs

LCI Databases

Key Data Challenges

1. Proprietary processes: Many specialty chemicals lack public LCI data
2. Regional variation: Same chemical produced differently in different regions
3. Temporal dynamics: Industry continuously improves efficiency
4. Supply chain complexity: Tracing feedstock origins is difficult

Regulatory Context

EU Regulations

REACH: Registration, Evaluation, Authorization of Chemicals

• Requires hazard and exposure information
• Life cycle thinking encouraged

Product Environmental Footprint (PEF)

• Several chemical PEFCRs developed or in development
• Standardized methodology for EU market

Plastics Strategy

• Recycled content requirements
• Design for recyclability

Industry Initiatives

Together for Sustainability (TfS)

• Chemical industry sustainability assessment program
• Includes carbon footprint guidelines

Operation Clean Sweep

• Preventing plastic pellet loss
• Not LCA but related environmental management

Key Takeaways

1. Chemical LCA requires careful attention to allocation in multi-output processes
2. Same product via different routes can have very different impacts
3. Bio-based isn't automatically better—land use impacts can be significant
4. Mass balance for recycled content is a chain of custody method, not physical composition
5. Industry associations provide free eco-profile data for major products
6. Regulatory pressure is driving standardization (PEF, REACH)

Resource List

Data Sources

• Plastics Europe Eco-profiles
• ecoinvent
• ICCA Global Chemical Life Cycle Initiative

Industry Organizations

• Plastics Europe
• American Chemistry Council
• Together for Sustainability

Guidance Documents

• PEF Category Rules for chemicals (various)
• ICCA guidelines on LCA

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Chemical LCA provides foundational data for most product assessments. When using chemical LCI data, verify allocation methods and regional appropriateness.