• Dr. Lee Anne Willson

Ames Greenhouse Gas Inventory

How does Ames contribute to climate change?

The Greenhouse Gas Inventory that the consultants Pale Blue Dot prepared last year gives us a good idea about the main sources of greenhouse gas emission for Ames, the first step in figuring out how to reduce those emissions. This report is available from the City of Ames Sustainability web page, https://www.cityofames.org/living/sustainability-in-ames/climate-action-plan. SSG, the consultants working on the Climate Action Plan, revised the list of sources; they added in half of the trips that are made to and from Ames each day (essentially assigning the other half to the origin or destination for each trip). That increased the emissions associated with transportation to nearly 40% of the total, and increased the overall emissions number from roughly 1.1 M to about 1.4 M tonnes/year. One reason this is so high is that housing in Ames is expensive compared to the surrounding communities, so many people who work here commute to Ames.

Figure: Numbers from the Pale Blue Dot study of greenhouse gas emissions for Ames. Each source will require a different set of actions to reduce emissions, and reduction in some sectors will lead to increases in others. For example, the city of Ames switched from coal to natural gas for the power plant at the end of Main Street; it derives power from burning some of our waste, but it needs a fuel to initiate and maintain that process. That lowered the coal emissions for Ames, but increased the natural gas portion, while lowering the total. ISU is planning to make the same switch in 2024. Our electricity comes from a variety of sources, and the mix is constantly changing. The plot (attached) shows what this looks like for a typical hot summer day; those days put the most strain on the system. From midnight to 5 AM more than half our electricity is typically coming from wind; from noon to 10 PM wind provides a bit more than 1/3 of the power. We can lower our emissions by running our dishwashers and washing machines between midnight and 5 AM – many of the newer models have an option for delayed start, so one need not wait up until after midnight to take advantage of the wind power peak.

Figure: Sources of electrical power for Ames over 24 hours on a hot summer day. The contribution to Ames electric power from solar is modest but growing. The city’s Sunsmart program is a way for anyone to help build solar power with a small investment. One powerpack costs $300 and gives a rebate on the monthly electric bill that is expected to more than pay for the initial investment over the next 20 years. Current technology is such that city-sized installations are actually a bit more efficient than home installations. See the post about solar energy potential for Ames for more on this topic. One of the most challenging pieces of the puzzle for Ames is how we manage our garbage. Currently the city recycles glass – big yellow bins at a number of locations around Ames – and it is important to keep glass out of the material that is burned for power. The city also provides containers for compostables, and is partnering with a team that will pick up your compost and leave you a clean pail, Core Living Compost, https://corelivingcompost.com/. The resource recovery plant has ways to recycle some other kinds of waste, as well. Most of our unsorted garbage goes to Resource Recovery where it is separated into burnable material, metals, and residue destined for the Boone County landfill. The part that is burnable – mostly plastics and paper – is burned in the power plant at the end of Main Street, where power is derived from the natural gas used to keep the process going and from the waste-derived fuel. Incinerating the burnable material leads to emission of CO2, both from the Waste Derived Fuel and from the gas used in the process. What goes to the landfill produces methane as it decays, so contributes to the greenhouse gas emission budget. The city has retained a consultant to carry out a study of options for managing waste going forward, as our waste-to-energy plant is reaching the end of its useful lifetime, and incinerating garbage may no longer be the best solution.