Why use EIO-LCA?

Two ways to do an LCA

Process-based LCA builds the product system from unit processes with measured inputs and outputs. It is precise about the product but stops where the analyst stops: purchases that are not modeled are left out. In this course that is SimaPro.

Economic input-output LCA uses the input-output accounts of the whole economy. Every sector's purchases from every other sector are known in dollars, so a demand for one sector's output can be traced through every supplier and the suppliers' suppliers, with no boundary cut. The price is resolution: every product in a sector carries the sector's average intensities.

Hybrid LCA combines them: process data for the foreground, EIO intensities from cost for the parts that have no process data. That is the method for term projects. Record which parts were estimated which way, and do not count an input twice.

How the model works

Let A be the direct requirements matrix: A_ij is the dollars of sector i needed to produce one dollar of sector j. For a final demand y, total output is x = (I − A)⁻¹ y = L y; the Leontief inverse L sums every round of indirect purchases. With B the emissions and resource use per dollar of each sector's output and C the characterization factors, impacts are C B L y. The model stores D = C B and N = D L; the Explorer multiplies the column of N for your sector by your dollars.

Assignment 3 Part I builds exactly this with ten sectors. The model here has 411 sectors and 23 indicators; the mathematics is the same. Sector j contributes D_ij L_js to indicator i per dollar of demand in sector s; the contributing-sectors table lists the largest of these terms.

What the numbers assume

• Linearity. Twice the dollars, twice the impact.
• Homogeneity. Every product in a sector carries the sector's average; a low-carbon concrete and an ordinary one are the same sector, and a design change inside one sector cannot be modeled.
• Price as the measure of quantity. The price year and basis change every number in proportion; the Explorer converts to 2012 producer dollars and shows the conversion.
• Vintage. The 2012 U.S. economy and inventories of about that year, not today's.
• Single region. Imports are represented with U.S. production technology.
• Cradle to gate. Use, maintenance and disposal are not included.
• Point values. No ranges; a sector average can differ from a specific product by a factor of two or more. Treat results as screening estimates and say so.

References

• Hendrickson, C., Horvath, A., Joshi, S., and Lave, L. (1998). Economic input-output models for environmental life-cycle assessment. Environmental Science & Technology 32(7), 184A–191A.
• Hendrickson, C. T., Lave, L. B., and Matthews, H. S. (2006). Environmental Life Cycle Assessment of Goods and Services: An Input-Output Approach. Resources for the Future Press.
• Ingwersen, W. W., Li, M., Young, B., Vendries, J., and Birney, C. (2022). USEEIO v2.0, The US Environmentally-Extended Input-Output Model v2.0. Scientific Data 9, 194.