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This is part two of a three-part series exploring the environmental lifecycle analysis completed by Divergent. It will get into some technical detail, but is intended for anyone who has an interest in total system environmental and health damages for manufacturing.

Before reading this section, please read our lifecycle analysis overview and Part 1 of this series.

Introduction to AP2

In Part 1, we introduced the Argonne National Lab’s GREET model. Developed over the last 20 years, it is a complicated and deep model that outputs greenhouse gas and particulate emissions.

AP2, formerly called APEEP, is a model developed by Nicholas Muller, Associate Professor of Economics at Middlebury College and Visiting Associate Professor at Carnegie Mellon University. AP2 takes the outputs from GREET and translates them into a dollar figure – the environmental and human health cost of those emissions.

From the AP2 website: “The Air Pollution Emission Experiments and Policy analysis (APEEP) model is an integrated assessment model that links emissions of air pollution to exposures, physical effects, and monetary damages in the contiguous United States. The model has been used in many peer-reviewed publications,” including a paper in Science in August 2014.

For example, in our recent analysis of various vehicle types, AP2 received a total CO2 count from GREET for the manufacture and operation of a vehicle. AP2 translated this CO2 count to an environmental and health system damage cost for the lifetime of the vehicle. To standardize this number, we then divided the cost across the total miles that car will be driven in its lifetime (estimated to be 160,000 miles per vehicle). The output from AP2 is then a cents (US dollars) per vehicle mile traveled (VMT).

History of GREET + AP2

The 2009 National Academy of Sciences report “Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use” used this same dual-model approach, connecting GREET and APEEP to show the combined damages. This report was one of the first to show the full lifecycle emissions of various types of vehicles and their environmental and health system cost. It revealed costs that were previously hidden, bringing into question some of the policies and trends in vehicle manufacturing.

This report was one of the founding inspirations for Divergent. Seeing this report, we believed we could and should do better: build a more environmentally sustainable car.

Connections between the GREET and AP2

GREET and AP2 have a fairly simple point of connection. We analyzed six vehicle types:

  1. Gasoline (25 mpg)
  2. Hybrid gasoline (40 mpg)
  3. Plug-in electric car (85 kWh)
  4. Plug-in electric SUV (85 kWh)
  5. Divergent compressed natural gas
  6. Divergent gasoline

For each of these vehicles, we used GREET to calculate greenhouse gas and particulate emissions over the lifetime of the vehicle, both for manufacture and operation. The chart below shows the conceptual connections between the models.

GREET and AP2 connections

We then used the outputs from GREET as inputs to AP2. The table below shows the most important outputs from GREET.

table of outputs from GREET

Using AP2, costs for each of the various pollutants were calculated and then tabulated. We also include the cost of the greenhouse gases directly, estimated by the US government at $39 per ton of CO2 equivalent.

table of outputs from AP2

The Vehicle production, Fuel production, and Operation lines under the Health Damages (per VMT) are the numbers that are used in the graph below.

cents per vmt graph

What’s next in this series?

In the next (and last) posting in this series, we’ll discuss the input variables to GREET, as well as our philosophy of changing as few of those variables as possible.

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