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This is part one 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, which sets the context for the discussion here.


My name is Nick Hofmeister. I have a computer science degree from Northwestern and an MBA from MIT. I’ve worked in fairly diverse industries, starting at Microsoft, followed by Bain & Co., an algae biofuels company, and three biotech/software startups I’ve founded. Over the years, my teams and I have raised about $260 million for early stage companies. I started making environmental analyses about 7 years ago to demonstrate the lifecycle value of a fuel made directly from a photosynthetic plant.

Why do we care about lifecycle analyses?

Around 2 billion cars have been built over the last 115 years; twice that number will be built over the next 35-40 years (Emmott, Stephen, Ten Billion, p. 95, New York, New York: Random House, Second Edition, 2014). The environmental and health impacts will be enormous. The automotive industry has $9 trillion a year in revenue and employs 11 million people.  And that doesn’t include oil & gas, a $4 trillion industry employing another 1.3 million people. These giants greatly affect the world’s material flows and all the consequences thereof. Unfortunately, very little has changed in the manufacture and use of vehicles in the last 100 years – our cars are getting bigger, heavier, and often less efficient at using energy. At Divergent, we intend to change this trajectory.


There are many types of environmental analyses, and they vary in both scope and kind. For this discussion, we are focused on environmental lifecycle analyses. Lifecycle analysis follows the path of an object through a system for its full lifetime, looking at its environmental impact at each stage of life. Lifecycle analyses can be performed on cars, toasters, a strawberry, or even a human being.

The exact scope of a lifecycle analysis is one of the trickiest questions: which parts of the life cycle do you include, and which not? For the strawberry, do you include the cost of making its fertilizer, the cost of its transportation to the grocery store, the cost of its disposal (e.g., the green tops, the rotten berries), and the cost of its packaging? The total cost of environmental and health system damages varies widely depending on the scope.

The gold standard in vehicles – GREET

In vehicles, thankfully, the Argonne National Lab has set the gold standard through a model called GREET (Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation Model). The first use of GREET was in 1995, and it has been peer- and industry-reviewed very thoroughly in the intervening 20 years. The scope of this model is quite wide – it looks at both vehicle operation and manufacture (vehicle cycle) and fuel manufacture and use (fuel cycle). It is also quite deep, capturing emissions down to the extraction and manufacture of materials (e.g., aluminum, lithium), as described in the image below:


The Argonne GREET model was also used for the 2009 National Academy of Sciences report “Hidden Costs of Energy: Unpriced Consequences of Energy Production and Use”, mentioned in the introductory article of this series).

What is the scope of GREET?

This model is very detailed and robust. It contains more than 100 fuel production pathways, such as corn ethanol, gasoline from algae, and cellulosic ethanol from switchgrass. It contains more than 70 different vehicle types, from a standard gasoline car, to an electric car, to a lightweight compressed natural gas vehicle.

GREET also looks backward into the manufacture of a vehicle quite deeply. As an example, consider the chassis of a vehicle. In GREET, even the transmission system (i.e., gearbox) is broken down into 8 major material types, each of which is accounted for separately in the model:  steel, copper, cast iron, magnesium, wrought aluminum, cast aluminum, average plastic, and rubber.

This level of detail, both in breadth and in depth, is necessary to create an accurate picture of the emissions of the vehicle across both its manufacture and its operation.

Inputs and outputs

GREET is free and publicly available for download. It is also, essentially, open source: if you download the Excel version, you can change any variable in the system that you wish.


However, to reduce the complexity in the model and variations in the answers, there are a limited number of inputs that are commonly changed. These include:

  1. Vehicle type
  2. Fuel type
  3. Total weight
  4. Balance of materials

Vehicle type has options such as standard internal combustion gasoline vehicle, electric vehicle, and lightweight compressed natural gas vehicle. Fuel type is tied with vehicle type, but there are many variations for each vehicle type. For example, an electric vehicle can use only electricity, but that could be electricity from the U.S. National Grid or from a coal-heavy region like the Midwest. A gasoline vehicle can use fuel with 15% corn ethanol or 5% cellulosic ethanol.

Total weight is a high-level, summarized factor that greatly affects the outcome of the GREET model. A Tesla Model S weighs approximately 4,700 pounds: every foot traveled by that vehicle is a result of moving 4,700 pounds of material. And at least 4,700 pounds of material needed to be manufactured in order to make the car (in reality, due to wasted materials, it is much more than that). In contrast, the Divergent Blade is 1,400 pounds, which makes it easier to move and easier to manufacture from an environmental standpoint.


There is also a common set of outputs created by GREET, showing the emissions of a vehicle across both its fuel cycle and its vehicle cycle. These are calculated on an energy/mile or grams/mile basis, depending on the output. Here are the most common outputs:

  1. Total energy
  2. Fossil fuels
  3. Coal
  4. Natural gas
  5. Petroleum
  6. Water consumption
  7. CO2 (VOC, CO, CO2)
  8. CH4
  9. N2O
  10. Total greenhouse gases (GHG)
  11. Volatile organic compounds (VOC)
  12. CO
  13. NOx
  14. Particulate matter large (PM10)
  15. Particulate matter small (PM2.5)
  16. SOx
  17. Black carbon (BC)
  18. Organic carbon (OC)

If you look at the examples included in GREET, it’s worth noting that a gasoline car uses a fair amount of natural gas. Why? Natural gas is used to make electricity, and electricity is used to make the materials that comprise a gasoline car and is used for its assembly. An electric vehicle typically uses a fair amount of coal, since coal is a major factor in the U.S. electricity grid.

What’s next in this series?

In the next posting in this series, we’ll discuss AP2 (formerly known as APEEP), which translates the output of GREET into environmental and health system damages.

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