Green Metrics, Clean Metrics

Climate Change Narratives

As the world struggles to put together even a minimally substantive climate change agreement in Copenhagen, a leaked analysis from the UN points out that annual GHG emissions will need to peak between 2015 and 2020, and decline thereafter, in order to eventually stabilize the atmospheric CO2 concentration at 450 ppm. This is the concentration at which the temperature increase is likely to stay within 2 deg C. Current pledges of maximum emission reductions and voluntary actions, if achieved, would still result in annual emissions in 2020 being about 1.9 Gt over the recommended limit. This gap increases to 4.2 Gt if the upper range of pledges are not achieved. If the peak occurs later than 2020, the CO2 concentration could exceed 550 ppm with a corresponding temperature increase of around 3 deg C -- based on the optimistic 1.9 Gt gap.

This is basically a case of a potentially very dire outcome coupled with weak solutions. Rosemary Randall writes that climate change discourses present two parallel narratives. Narratives about the problem of climate change suggest losses on a terrifying scale that may happen far in the future or in distant lands. Narratives about solutions revolve around bland and ineffective solutions, mostly ignoring the scale of potential losses in the future. Ineffective solutions are not just the domain of governments -- a recent AP-Stanford University poll shows that three-quarters of respondents would support action to address climate change, but 59% wouldn't support any action if it costs them an additional $10 a month on electricity charges (which by the way is just about what it costs extra to purchase green electricity where I live).

The disconnect between the scale of the problem and the effectiveness of the solutions is alarming.

Kumar Venkat

Role of Forests in Climate Change Mitigation

A very interesting front-page article in The Oregonian on the science and politics of using forests to mitigate climate change. It turns out to be a complex optimization problem. Trees, of course, sequester carbon, but thinning out the stands might help store more carbon in the long run by reducing the intensity of forest fires. On the other hand, letting young trees mature would actively take carbon out of the atmosphere during the growth phase. Logging mature trees and turning them into lumber could store carbon in long-lived wood products (of course, some carbon would be released from decomposition or burning of waste generated during logging and manufacturing). Undisturbed soil under forest cover could store significant amounts of carbon for long periods of time. My guess is that the right way to structure a forest will vary from place to place, depending on the tree species, climate and a host of other factors. Has anyone formulated this as a proper optimization problem?

Kumar Venkat

Carbon Footprint of Social Networking

Facebook just announced that it now has over 350 million users with half of them logging on to the site on any given day, and the average user spends over 55 minutes a day on Facebook. Plus, 55 million status updates are posted every day and 2.5 billion photos are uploaded each month. Very impressive, but I have often wondered about the environmental impact of social networking. Using carbon footprint as a proxy for overall environmental impact, here is a quick back-of-the-envelope calculation.

The number of user-hours per day is about 160 million (assuming 55 minutes/day/user). I found a CO2 emissions estimate of 20 mg/second for basic web browsing, most of it coming from the electricity consumed by the visitor's computer. I independently verified this by assuming 100 W of power consumption for a typical desktop computer and monitor in active mode, which translates to roughly 20 mg of CO2e per second for US average electricity (cradle to grid). Electricity emissions vary around the world, but the US emission factor is a typical value. For a first-order estimate, I decided to count only the time that users are logged on to Facebook and actively using their desktop computers, ignoring their Facebook activities like status updates, uploads and downloads that will consume additional energy in the network infrastructure and data centers.

Putting all this together works out to 4.2 million metric tons of CO2e per year for all Facebook users. (The actual emissions are likely to be higher, but that depends on a lot of factors ignored here.) This carbon footprint is equivalent to the annual emissions from a million passenger cars in the US.

I know, it is not fair to focus just on Facebook, but I am just using it as an example to understand the footprint of social networking today and how this might change if someday 3-4 billion people end up on social networking sites. I will get back to this topic soon and report on a more rigorous, defensible analysis. For now, this remains a quick-and-dirty initial estimate and a starting point for further exploration.

Kumar Venkat

Low Carbon Fuel Standards

A number of states are considering a Low Carbon Fuel Standard (LCFS) following California's adoption of its own standard earlier this year. An LCFS regulates the carbon intensity of transport fuels. It reaches as far upstream into the fuel supply chain as possible and focuses on the relatively small number of oil refiners and importers.  Each company works under the constraint of a maximum carbon intensity (g of CO2e per MJ of fuel energy). This cap declines annually in order to reduce total emissions, and allows trading of emission credits between oil refiners, biofuel producers and electric utilities. Adding the right biofuels to the mix could reduce a suppliers average carbon intensity. This, of course requires a full life-cycle assessment of each fuel (well to tank + tank to wheels, including challenging issues such as co-product allocation and indirect land-use changes) in order to establish its carbon intensity. This is the first public policy initiative that codifies life-cycle assessment principles into law! More in an excellent article by Sperling and Yeh in Issues in Science and Technology.

Kumar Venkat

Carbon Footprints of Lighting Products

The future of lighting is likely to be LED based. A life-cycle assessment study by OSRAM Opto Semiconductors compares the life cycle environmental impacts of three types of lamps: a 40W incandescent lamp, an 8 W compact fluorescent lamp (CFL), and an 8 W LED lamp with 6 LEDs -- compared on the basis of luminous flux (345-420 lumen) as well as color temperature and rendering, and a lifetime of 25,000 hours. This translates to 25 incadescent lamps, 2.5 compact fluorescent lamps and 1 LED lamp. Here are their results in Kg of CO2e:

	Manufacture	Use
Incandescent	3.5	564
Compact fluorescent	2.2	113
LED	2.4	113

The use phase dominates (manufacturing contributes less than 2% of life-cycle GHG emissions) and the LED lamp is competitive with CFL based on current technologies.

Kumar Venkat

Carbon Footprint of Electric Motors

Our recent work on the carbon footprint of industrial electric motors (specifically for NEMA premium motors) shows that the production emissions are well within 1% of the total life-cycle GHG emissions. The use phase is responsible for most of the emissions. Compare this to systems like computers, where significantly more knowledge is embedded in the product (which makes the production more intricate and complex) and the production share of the carbon footprint is much higher (for example, 44% for the 20-inch iMac). But the sheer bulk of a large industrial motor makes its absolute carbon footprint much higher than that of a desktop computer.

Kumar Venkat

Diet and Global Warming

I spoke with Carrie Sturrock at The Oregonian about carbon foodprints -- in particular, comparing meats and vegetarian foods. Her PDX Green column is at http://blog.oregonlive.com/pdxgreen/2009/11/carnivore_offers_plain_truth_f.html .

Kumar Venkat

Carbon Footprint of Computers

As I previously noted, Apple's 20-inch iMac has a life-cycle carbon footprint of 870 Kg of CO2e. Of this, 382.8 is from production and 435 from a 4-year use phase. Apple doesn't explain the methodology, though. For a sanity check, I looked at a 2004 paper by Eric Williams which uses a hybrid (process + economic IO) LCA method to compute the energy intensity of computer production. Mapping his electricity consumption to US average (not that much production takes place here) and all direct fossil fuel to natural gas (might be too optimistic), and using our internal LCI data for electricity and natural gas (from CarbonScopeData), I have 321.44 Kg of CO2e for a desktop computer with a 17-inch CRT monitor and 733 MHz processor produced in 2000 -- the carbon footprint is very close to the 20-inch iMac's. The iMac, of course, runs a 3.06 or 3.33 GHz processor -- much better performance at nearly the same footprint as the older machine, assuming the methodologies are comparable.

Next question: Assuming an average useful lifetime of 4 years, does it make sense to replace your computer with a more energy-efficient machine before the 4 years are up?  Using the iMac example, if you bought a newer computer (consuming 20% less energy in the use phase and similar production phase energy use and carbon emissions) after only 3 years of using the existing one, it would take 4 more years (the entire use phase of the new computer) to just break even on total carbon emissions. This assumes that the old computer is recycled or sits in your garage.

Computer production is very energy and carbon intensive, so it makes good carbon sense to use our old computers as long as possible before getting new ones.

Kumar Venkat

Carbon Footprint of US Healthcare

Health care activities contributed 8% of US GHG emissions in 2007, according to the Nov. 11 issue of the Journal of the American Medical Association. A study by Chung and Meltzer quantifies the carbon footprint of the US health care sector using the Environmental Input-Output Life Cycle Assessment model developed at the Carnegie Mellon University and 2007 data on health expeditures. In comparison, the  National Health Service contributed 3% of UK's CO2 emissions (percentage of GHGs might have been slightly higher). Reducing the carbon footprint of health care will require finding leverage points in the health care delivery supply chains where net health benefits can be maximized while minimizing environmental damage.

Kumar Venkat

GHG Emissions from Deforestation

In today's New York Times, Thomas Friedman makes the point that annual GHG emissions from the clearing of tropical forests exceed the total emissions from the entire global transportation sector. It is well-documented that tropical forest clearing accounts for 18-20% of anthropogenic carbon emissions and destroys globally significant carbon sinks (Gibbs, et al; Meridian Institute). As the Meridian report points out, forests will contribute to climate change mitigation only if their value increases to a level that makes protecting forests consistent with viable development strategies. After visiting a Brazilian community that lives in and off the tropical forests, Friedman reaches the same conclusion: To save an ecosystem of nature, you need an ecosystem of markets and governance.

In a way, this is really a large, low-hanging fruit as far as cutting GHG emissions immediately. But it is contingent on developing sustainable livelihoods for people that depend on tropical forests for food, materials and land. It is impossible to separate economic sustainability from environmental sustainability (my 2004 article on this).

Kumar Venkat