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How Much Greenhouse Gas Does SCU Emit

Sophia Huang

At Santa Clara University, we are more than just aware of climate change – we are taking action. We, the university, have a formal climate action plan to become climate neutral by the end of 2015. That means that we will be reducing our greenhouse gas emissions and offsetting them with renewable energy certificates. How successful we are depends on the entire university’s actions, meaning all staff, faculty, and students. Being climate neutral is part of the university’s goal in being socially responsible and educating the next generation. When we reduce our greenhouse gas emissions, we are not only helping Santa Clara University, we are participating in the creation of a global, climate-responsible lifestyle that ensures a sustainable future.

Before we can decide how to cut our greenhouse gas emissions, we will need to know how much SCU is emitting with all our activities. Here, I will focus on two categories: wastewater and solid waste. I’ll examine how each category produces greenhouse gases (GHGs) and see how much SCU is producing in a year.

Some emissions categories do not directly emit CO2, but still have the potential to cause global warming. Gases like methane (CH4)­­ and nitrous oxide (N2O) can retain solar radiation and increase atmospheric temperatures over time just like CO­2. This ability is called the global warming potential and is converted for non-CO2 gases into CO2 equivalents.

Emissions from Wastewater Treatment
When we take a shower or do the laundry, the water flows through pipes to a local sewage treatment plant. For SCU, all our wastewater goes to the San José-Santa Clara Regional Wastewater Facility, which sends treated water to the Bay and 13 percent to South Bay Water Recycling. During the treatment process, bacteria decompose organic matter and emit GHGs as a byproduct. The types of GHGs they produce depend on the treatment type.
There are two basic treatment types, aerobic and anaerobic.

Treatment TypeOxygen Present?  GHGs Produced
Aerobic Yes mostly CO2
Anaerobic No CH4, N2O

The San José-Santa Clara Regional Wastewater Facility uses anaerobic treatment, and some of the natural gases produced are used to generate electricity in a treatment called anaerobic digestion. This process significantly lowers the GHG emissions from wastewater treatment because some of the GHGs are captured and used for power generation, instead of emitted and wasted. The amounts of CH4 and N2O that are still emitted are each multiplied by their respective global warming potentials to yield their equivalents in CO2. This makes the values of all emissions reports comparable.

Chemical100 Year Global Warming Potential

CO2

1

CH4

25

N2O

298

Source: IPCC (Intergovernmental Panel on Climate Change)

So how much water is SCU using in a year? If we consider the major water uses of a person, then toilets, washing machines, and showers will top the list. A toilet uses 1.6 gal of water per flush, and the average American flushes about 5.6 times a day. That would mean almost 9 gal a day, and 63 gal a week. The table below shows how much water one person uses for certain activities in the course of a week and of a year.

Source of Water UseWater Usage each Time (gal)Water Used in a Week (gal)>Water Used in a Year (gal)

Showers

20

140

7,280

Toilets

1.6

63

3,270

Washers (top load)

45

45

2,340

Washers (front load)

25

25

1,300

SCU’s total water usage is composed of everyone’s water usage from activities like those in the table above and of other uses, like landscape irrigation. The total amount of water we, as a campus, use in a year is about 74,800,000 gal. Emissions from this wastewater are a result of the treatment process, when organic waste is decomposed by bacteria. Chemical treatments, infrastructure and transport, and energy consumed in the process are currently not considered. When our wastewater is treated at the San José Water Pollution Control Plant, 86,000 pounds of CO2 equivalents are produced. This is the same amount of CO2 that’s produced by driving a car 104,622 mi, enough to circle the Earth’s equator 4 times.

Emissions from Solid Waste
At SCU, the solid waste we produce includes construction waste, yard trimmings, food scraps, and anything that ends up in the trash. This solid waste can be disposed of in many ways: composting, recycling, incineration, and landfilling. The last two options produce GHGs depending on if the garbage is burned or left to decompose.

Waste Disposal MethodGreenhouse Gases Emitted
1. Incinerated Waste (off-campus) CO2
2. Landfilled Waste
  1. No CH4 Recovery
  2. CH4 Recovery & Flaring
  3. CH4 Recovery & Electricity Generation
CH4

The garbage you throw away ends up at Newby Island Landfill in the city of Milpitas where the waste slowly decomposes. It does so mostly in the absence of oxygen because of the lack of air circulation in the landfills. This leads to anaerobic decomposition, which emits CH4 instead of CO2. Thus, CH4 is the only landfilled waste GHG accounted for. At Newby Island Landfill, they flare half of the CH4 produced and use the other half for power generation, much as the wastewater treatment plant does.

In a year, the average student or staff member at SCU tosses 380 lbs of trash into the trash bin. About 58% of this is either recycled or composted, so 160 lbs per person, or 1.5 million lbs for the entire campus, remain to be sent to Newby Island Landfill. When we consider the total amount of waste produced by SCU that's landfilled, 1.8 million lbs of CO2 equivalents are emitted in a year. This amount of CO2 takes up a volume of 16 million ft3. The average, newly-built American house has a volume of 16,000 ft3, so SCU produces enough CO2 to fill almost 1,000 homes with CO2.

Conclusion
Provided above is a general background on how SCU’s greenhouse gas emissions for wastewater and solid waste are calculated. These categories are included by some institutions in their climate action plans to reduce or offset the emissions. At SCU, we are striving for net zero emissions, but we are also looking beyond the numbers.  As an educational institute, our goal is to cultivate sustainable lifestyles and ethical values. We hope that this will be embedded people’s everyday actions, resulting in better decisions and creation of a more sustainable world.

Sophia Huang is an SCU student and environmental ethics fellow at the Markkula Center for Applied Ethics.

 

 

Feb 1, 2015