Sustainability

Although climate change is the center of many political debates, the warming of Earth’s climate system is a widely accepted fact in the scientific world. Ninety-seven percent of “actively publishing climate scientists” agree that Earth’s climate is changing due to human activities (NASA 2018). The atmosphere’s carbon dioxide (CO₂) levels as of December 2024 are 420 parts per million (ppm), which is the highest measurement in the past 800,000 years (NASA 2018). Before the industrial revolution, Earth’s CO₂ levels fluctuated between roughly 180 ppm during ice age periods and 280 ppm during interglacial periods (NASA 2018). These rising and falling CO₂ concentrations represent the natural changes that occur during the 100,000-year Milankovitch cycle. In comparison, the current level of 420 ppm represents uncharted territory. Because of this unprecedented concentration of CO₂, scientists do not know exactly how these high levels will affect humanity and life on Earth. However, scientists do know that throughout climate history, temperature is directly correlated with atmospheric CO₂ levels (NOAA 2008). When graphed, temperature and CO₂ follow each other closely.

CO₂ is just one of the GHGs in the atmosphere that contributes to Earth’s warming. Other GHGs include nitrous oxide, methane, water vapor, ozone, and synthetic chemicals. GHGs have a warming effect due to their ability to trap heat in the atmosphere. GHGs in Earth’s atmosphere absorb infrared radiation emitted from Earth’s surface and also re-emit infrared radiation, commonly known as heat. The greenhouse effect refers to the natural process of infrared radiation being absorbed by GHG molecules, and then re-emitted in all directions, some of which is directed back towards Earth. Without naturally occurring greenhouse gases, Earth's average temperature would be near 0°F (or -18°C) instead of the much warmer 59°F (15°C) (NASA 2010).

However, since the Industrial Revolution, the burning of fossil fuels and other human activities such as deforestation has led to a dramatic increase in the concentration of GHGs in the atmosphere. GHGs that have high global warming potential have a long residence time in the atmosphere, absorb effectively in the infrared part of the electromagnetic spectrum, and have a relatively high concentration in the troposphere (lowest layer of the atmosphere). Once GHG molecules absorb infrared radiation, they collide with and transfer kinetic energy to other molecules in the atmosphere such as nitrogen and oxygen, which increases the temperature of the atmosphere. As the concentration of GHG molecules in the atmosphere increases, more energy is trapped. In this way, GHGs act as a “blanket” and prevent heat energy from escaping back out to space.

Scientific research published in peer-reviewed journals shows that the current CO₂ levels in Earth’s atmosphere have been rising since the industrial revolution (UC San Diego 2017). Human activity is also responsible for the release of methane, nitrous oxide, and other potent GHGs (Keeling 1997). Humans are already experiencing the effects of a warmer climate through more extreme weather events, increases in pests and disease, devastation to wildlife habitat, heat stress, increased drought, increased costs, and displacement of people which disproportionately affects under resourced communities. (Keeling 1997). Arguably, the most concerning part of global climate change is that it is extremely difficult to reverse. Now that there is momentum in Earth’s warming, the extent of sea ice is diminishing, sea levels are rising, oceans are warming, and glaciers around the world are melting. Further, these events lead to positive feedback loops that amplify warming. Due to climate change momentum, it will take hundreds of years for GHG concentrations in the atmosphere to return to preindustrial concentrations. For these reasons, we need to take responsibility for emissions coming from the SAU 70 community and implement this CAP immediately.

The HHS Environmental Club gathered data for each of the schools in the SAU 70 to create a GHG inventory. This was accomplished by researching building energy use, tons of solid waste generated, gallons of wastewater generated, gallons of water consumed, and energy use for transportation which includes school bus routes, employee commute and student commute. In the HHS CAP, an additional sector labeled “Other Travel” includes data relevant only to the high school. This data was used to calculate the GHG emissions from each sector in MTCO₂e and is summarized in Table 1 below.

An important aspect of GHGs is the unit of measurement used to estimate emissions. While CO₂ is the primary GHG released by human activity, more potent GHGs including methane and nitrous oxide are also released. To simplify the discussion and comparison of these emissions, CAPs use a metric known as carbon dioxide equivalents (CO₂e). The CO₂e metric translates each GHG to an equivalent mass of CO₂ by taking into account its relative global warming potential. Methane and nitrous oxide are 25 and 310 times more potent per molecule respectively, than CO₂ in their abilities to trap heat in the atmosphere (DES 2009). Converting these GHG emissions into CO₂e makes it easier to communicate how GHG emissions contribute to climate change by using a standard unit of measurement.

Measuring GHG emissions is a critical first step in developing the CAP. First, the GHG inventory identifies major sources and quantities of GHG emissions associated with the activities and choices currently made by all schools in SAU 70. Second, the inventory, along with population projections, provides the baseline that is used to forecast emission trends and to develop an accurate near-term emissions reduction target consistent with State objectives.

GHG emissions from the 2022-2023 school year were prepared for SAU 70’s operations. The 2022-2023 school year inventory shows that SAU 70’s operations generated 2,987 MTCO₂e. SAU 70’s GHG inventory is broken down into the following seven sectors.

Building Energy

The building energy sector includes GHG emissions generated from electricity consumption and fossil fuel consumption at each school within SAU 70, and transportation for wood chips for HHS. The GHG emissions include only anthropogenic sources. Anthropogenic CO₂ comes from human actions in which fossil fuels are burned. This carbon is part of the long-term carbon cycle. When humans burn fossil fuels, the CO₂ concentration in the atmosphere increases which contributes to climate change (EPA 2024b). The carbon atoms in biogenic CO₂ are in a short-term carbon cycle and are therefore not included in this CAP. Biogenic CO₂ is released by the combustion or decomposition of natural and organic matter (EPA 2017).

Employee Commute

Employee-generated GHG emissions associated with gasoline, diesel, and electricity consumption from vehicle trips and vehicle miles traveled during employee commute.

Student Commute

Student-generated GHG emissions associated with gasoline, diesel, and electricity consumption from vehicle trips and vehicle miles traveled during student commute.

School Buses

School bus-generated GHG emissions associated with diesel consumption from school bus routes.

Solid Waste Generation

Solid waste sector emissions include the methane emissions from the decomposition of waste generated by staff and students at the Lebanon Landfill.

Wastewater Generation

Wastewater treatment results in GHG emissions associated with the electricity consumed during treatment, as well as fugitive methane emissions resulting from the treatment process for wastewater.

Water Consumption

Water-related GHG emissions are associated with the energy and fuel used to convey, distribute, and treat water used at each school in SAU 70.

Other Travel

Other travel is emissions relevant only to HHS and includes emissions associated with staff professional development activities, the March Intensive program, field trips, school buses used for athletics at HHS, and maintenance vehicles.

Figure 4 shows the breakdown of SAU 70’s GHG emissions in the 2022-2023 school year. The greatest source of emissions stems from building energy and represents 36 percent of the total emissions. Employee commute represents the second highest emission sector at 32 percent, and student commute represents 17 percent of total emissions. GHG reduction measures can be found in section 5 of this CAP.

Figure 4.  SAU 70 2022-2023 School Year Greenhouse Gas Emissions Inventory by Sector

The following GHG emission reduction measures will help SAU 70 and its schools meet their 2030 GHG reduction target and make significant progress towards meeting their longer-term 2050 goal. The GHG reduction measures are divided into priority measures and secondary measures. The measures were derived from building energy audits conducted for each school, ideas generated by students at workshops, staff input, and the 2022 HHS CAP.