Editor’s Note: This is the first installment in a series exploring climate solutions proposed by Purdue students and experts across the country.
For Purdue to mitigate its contribution to climate change, some students say the university must find a carbon neutral way to power its campus.
A group of engineering students spent the last year developing a climate action plan for Purdue. The plan, which was released on Sunday, offers ideas for how Purdue can transition to be carbon neutral over the next decade while showing it is financially viable.
The students estimated that Purdue’s transition to carbon neutrality would save the university about $11 million within 10 years, as compared to the student-estimated amount Purdue already spends on energy.
“The purpose of the plan is to show Purdue that it is possible,” said Anika Bhoopalam, a sophomore in the College of Engineering and lead contributor to the plan. “If students could create this plan, then Purdue could definitely create a carbon neutrality plan for themselves, and hopefully (our plan) inspires them to do so.”
The students said they hoped their plan can serve as a starting point for Purdue to build on in the future.
The current energy infrastructure
The four smoke stacks that can be seen on the southside of campus mark the location of Wade Utility Plant.
Inside one coal and three natural gas boilers burn fossil fuels to heat, cool and produce about half the electricity used by Purdue. The rest of the campus electricity is bought from Duke Energy, a major energy provider in Indiana, according to previous Exponent reporting.
The Wade Utility Plant emitted more than 310,000 tons of CO2 equivalent in 2019, according to its mandatory reporting to the Environmental Protection Agency. Carbon dioxide equivalent reports global warming potential of different greenhouse gasses in terms of CO2. The CAP (climate action plan) estimated the electricity Purdue purchased from Duke produced another 327,876 metric tons of CO2e.
This brings the estimated footprint of Purdue energy consumption to 637,876 metric tons of CO2e for 2019, an amount equivalent to burning over 700 million pounds of coal, according to the EPA’s greenhouse gas equivalency calculator.
Wade Utility Plant’s four boilers turn water into steam, turning a turbine to create electricity, according to Purdue’s physical facilities website. The steam is also used to heat or cool campus buildings through a network of underground pipes.
In the winter, steam from the plant is pumped to the buildings to heat them. In the summer, the steam is instead used to run a chiller system, and cold water is pumped to cool the buildings.
Physical facilities declined to be interviewed for this story, but a representative said they would provide more information about Purdue’s energy infrastructure in an email once Purdue has a chance to review the CAP.
Alternative fuels for Wade
The students’ CAP proposes solutions that are tailored to the energy infrastructure already on campus, so Purdue would be more open to adopting them, Bhoopalam said.
“Carbon neutrality is not that all Purdue’s energy infrastructure has to be 100% renewables,” she said. “At least not right now, because that would be a big shift. Especially because the Wade Utility Plant is so central to Purdue’s energy infrastructure.”
The CAP explores burning alternative fuels in the power plant to replace fossil fuel use. These solutions allow Purdue to reduce emissions while continuing to use the boilers.
Purdue’s coal boiler can burn solid fuels, so it could theoretically burn non-fossil solid fuel. One idea proposes that the coal boiler should switch to tire-derived fuel (TDF), in which waste tires are shredded and burned.
TDF produces more heat per pound than coal, the CAP says, powering campuses while diverting used tires from the landfill. The students estimated TDF would reduce emissions from the coal boiler by 25 percent.
The coal boiler would also be able to burn biomass, a form of fuel derived from recently living plant tissue like wood, crop residues or wood chips. However, the students concluded that biomass isn’t available in the needed quantities near West Lafayette.
To address this, the CAP recommends bio-oil, another type of biologically-derived fuel for use in the natural gas boilers.
Bio-oil is a petroleum-like fuel created from biomass. Robert Brown, a mechanical engineering professor at Iowa State, researches fast pyrolysis, the process used to create bio-oil. During fast pyrolysis, biomass is rapidly combusted in a low oxygen environment. Under these conditions, the biomass produces vapors that can be condensed into liquid fuel, he said.
This high-density fuel can be easily transported and directly burned in the boiler, Brown said, though the boilers would need a minor modification to their burners.
Brown said he is particularly excited about bio-oil for its potential as carbon-negative energy. His research suggests it’s possible for bio-oil to pull more carbon out of the atmosphere than it releases.
Since the bio-oil is derived from recently-living organisms, the carbon contained in the tissues came originally from the atmosphere. In other words, the carbon that is released by the combustion of bio-oil is part of a natural carbon cycle, and it doesn’t contribute net greenhouse gas emissions to the atmosphere.
Then there’s biochar, one of the byproducts of fast pyrolysis. It’s a charcoal-like substance that can be added to soil to store carbon for long periods of time.
Biochar can help mitigate climate change by reducing the amount of CO2 in the atmosphere. According to Brown’s research, this makes bio-oil a carbon-negative fuel.
“When you purchase that bio-oil,” Brown said, “it doesn’t have a positive carbon coupon attached. It’s got a negative carbon coupon attached.”
Burning bio-oil in the boilers would displace fossil fuels while the negative emission credits may be able to chip away at other sources of university emissions. The downside, Brown said, is that bio-oil is more expensive than traditional fossil fuels.
Renewable energy capacity on campus
With alternative fuels reducing the emissions associated with the Wade Utility plant, the CAP describes ways to reduce the emissions from the electricity Purdue purchases for Duke Energy.
Only 2% of the electricity Duke Energy produces is from solar, wind and hydropower, 37% is from nuclear with the rest coming from fossil fuels, according to its website.
To decrease Purdue’s reliance on non-renewable electricity, the CAP recommended building solar and wind renewable energy production on and around campus.
For solar, students propose installing solar canopies over parking lots on campus. This would allow Purdue to build out renewable energy capacity without taking up valuable campus real estate, the students said.
The CAP identifies nine parking lots and six campus roof tops that would likely be suitable for solar energy. If solar was installed in all locations it could replace 6% of Purdue’s annual electricity use with renewable energy.
For wind, the students proposed building 55 wind turbines on rural university property in collaboration with Duke Energy. The CAP did not specify which properties.
There are some issues with Purdue installing significant renewable energy capacity. As a non-profit public institution, the Indiana Utility Regulatory Commission limits how much capacity it can install, said Robert Koester, a professor involved in climate planning at Ball State University.
“By definition, a university cannot become a utility. (It) cannot produce power for export,” Koester said. “We can only produce power to downsize our (electricity) demand on the grid.”
If a university installs too much renewable energy capacity, it risks electricity production outstripping university electricity demand.
BSU has grappled with this regulatory challenge as it works towards its aggressive 2030 carbon neutrality goal. To avoid this logistical issues of on-campus production, BSU is exploring a Virtual Power Purchase Agreement. Under a VPPA, the university enters into a contract with a separate energy utility to build a new renewable energy project.
“Because we caused the project to happen, we still own the non-pollution rights to the property,” Koester said. “So we get to claim the non-pollution against our brown power consumption. It’s a paper accounting thing.”
By supplying a new source of green energy to the grid, the VPPA would offset the fossil fuel-intensive electricity, which is known as brown power, that the university buys from the Indiana energy providers.
Though BSU’s campus might be separated from the renewable energy project by hundreds of miles, it still receives credit for the emissions reductions of the project. This arrangement allows BSU to continue to work towards its carbon neutrality goal without violating utility regulations.
Purdue would likely have to use a VPPA if it invested in a massive wind project in collaboration with Duke Energy as the CAP recommends.
While a VPPA is one way to reduce emissions, Brown said there was a similar accounting mechanism that is used for natural gas that Purdue might explore. Natural gas comes from fossil fuel extraction, but gas pipelines can also accept biogenic methane from biogas projects.
Biogas is methane derived from the decomposition of organic materials. Both natural gas and biogas are mostly methane gas, making them equivalent as fuels.The central difference is that biogas has much lower net CO2e emissions footprint.
If biogas is pumped into a natural gas pipeline, it displaces fossil natural gas and reduces the overall greenhouse gas emissions associated with a natural gas pipeline.
The rights to these prevented emissions can be purchased to offset the emissions associated with a power plant burning fossil natural gas, like the Wade Utility Plant.
Brown said there are biogas projects across the Midwest that capture biogas from manure lagoons. Further out west, California buys the rights to that renewable natural gas as part of its strategy to reduce emissions.
“We are now paying farmers to put those biogenic methane molecules into the pipeline,” Brown said.
Purdue could continue to burn natural gas in its boilers and offset those emissions using renewable natural gas credits. This would allow Purdue to continue work toward carbon neutrality without needing to locate a biogas project on campus.
Beyond the plan
Koester and Brown have several other ideas that Purdue could explore to transition to carbon neutral energy infrastructure.
A major part of the energy transition at BSU has been shifting their campus to geothermal heating and cooling. Koester said Purdue could take the same approach by installing geothermal systems incrementally.
Purdue could start by installing geothermal systems in all new buildings, while transitioning older buildings a couple at a time. Overtime, the amount of buildings receiving heating and cooling from the Wade plant would decrease.
“(You) work your way toward reduced demand of your central system to the point where then it would be cost effective in the future to swap out the combustion system with a geothermal for what remains,” Koester said.
The issue with installing geothermal is that it would likely require substantial change to Purdue’s infrastructure. For instance, BSU’s geothermal system required drilling 3600 bore holes, needed to extract heat from the earth, among other investments.
To avoid such a significant disruption, Brown said Purdue might explore a giant centralized heat pump that could replace the four boilers at Wade Utility Plant.
“It’s really simple: think of air conditioning and just run it in reverse,” Brown said. “So an air conditioner is going to take heat out of your building and pump it outside. You’ll notice inside you have these cold coils and outside you’ll feel the heat. Imagine just turning that around and pumping heat into the house.”
The heat from this giant heat pump would replace heat generated by the fossil fuel boilers. That heat could then be used to heat and cool the campus using Purdue’s existing distribution system.
With this option, rather than install individual heat pumps all across campus, Purdue could install one system and distribute heat from a central location.
“Now whether that makes economic sense, I don’t know,” Brown said. “But it certainly seems like it would be compared to completely replacing infrastructure across the whole university.”
Editor’s Note: This reporting is supported by Carbon Neutral Indiana, a nonprofit helping “individuals and businesses clean up their carbon footprints.”