Holy Cross and Clean Heat: Options, Obstacles and Answers
In 2007, the College of the Holy Cross joined the American College and University Presidents Climate Commitment. This decision bound the College to a promise: it would be carbon neutral by 2040, meaning that the College would produce net-zero carbon emissions by that date. Eight years later, the College has made substantial and, indeed, remarkable progress towards achieving that objective. According to Holy Cross’ report on emissions for fiscal year 2014 (published in May 2016), the College has reduced its emissions by 44.65% relative to 2007 levels—from 23,056 metric tons of carbon dioxide equivalents (MTCDE) in 2007 to 12,761 tons MTCDE in 2014. On the surface, it appears that Holy Cross is well on its way to reaching carbon neutrality by 2040; with 23 years to go, we’re basically halfway there!
As is typically its wont, the truth is a bit more complicated. Breaking down the sources of the College’s remaining emissions will help clarify where we actually are on the path to carbon neutrality. In 2014, the emissions breakdown was as follows: 0.1% came from “refrigerant use & reclamation”; 1.2% came from “air travel”; 2.3% came from “institution owned & controlled vehicles”; 26.9% came from “commuting (students, faculty & staff)”; and the remaining 69.5% came from on-campus stationary source fuel use." If you noticed that electricity was not mentioned, that’s because Holy Cross is able to count its purchased electricity as producing zero emissions because that electricity is generated by hydroelectric dams. As Alif Kanji ‘18 discusses here, there are reasons to be skeptical of that method of accounting. However, the purpose of this article is to focus on that last number: the 69.5% of Holy Cross’ remaining emissions, the 9,075 tons of MTCDE, that come from the boiler plant, our source of heat on campus.
The College’s boiler plant runs on natural gas, which is by far the cleanest fossil fuel. In fact, a substantial portion of the College’s emissions reductions came from the decision to power the plant with natural gas as opposed to fuel oil. While emissions from our heat usage could be reduced by making our systems more efficient—and efforts to eliminate wasted heat are thus worthwhile—it will take a lot more than improved efficiency to reach carbon neutrality.
This state of affairs drove a research project you’re probably tired of hearing about by now and, if you haven’t heard about it yet, you can here, here, here, or here. A major focus of this research was determining what clean, renewable heating alternatives are available for the College to use as replacements for our fossil fuel-powered boiler plant. To that end, we investigated the viability of solar thermal, biomass gasification, waste to energy (WTE), and geothermal heat pump (GHP) systems. At the end of this research, we concluded that a GHP system would be the best option to pursue in order to eliminate the College’s remaining emissions from heating. The easiest way to show why this is the case is to highlight the shortcomings of the other options.
First, solar thermal is an inadequate source of heat to meet the needs of the College. Different from solar photovoltaic systems, which produce electricity, solar thermal systems use vacuum sealed tubes which focus sunlight to heat water that is then used to heat buildings. The root of the issue with solar thermal power is its inability to provide heat on demand. Unlike electricity, which can be stored in batteries or sold back to the power grid, heated water can only retain energy for a limited period of time. Therefore, during a blizzard—when heat demand is high and sunlight is nonexistent—a solar thermal heating system would not be able to provide enough heat for the entire College. Furthermore, solar thermal’s peak efficiency is inconsistent with the needs of the College. This system produces the most heat when it is needed the least: the summer. Due to these inefficiencies, a solar thermal heating system would not be a cost-effective investment for the College, and it would not eliminate the remaining emissions from heating.
Another heating source that could replace Holy Cross’s natural gas boiler and reduce emissions is a biomass gasification generator. Biomass gasification is the process of heating organic matter (such as wood chips) under tightly controlled conditions to produce heat with virtually zero carbon emissions. In order to investigate this technology, a research team visited Middlebury College to learn about their biomass gasification generator. Middlebury is able to acquire truckloads of wood chips from the local area that are used to fuel their biomass gasification machine. This supports the local economy and provides essentially emissions free heat, but also only supplies Middlebury with about 30% of its heating needs. In order to obtain the other 70%, Middlebury uses fuel oil, a fossil fuel with higher emissions than the natural gas used at Holy Cross. Due to large upfront costs, maintenance costs, and the inefficiencies of biomass gasification, we rejected this heating option as a viable solution to Holy Cross’s heating problem. While innovative, this system would also fail to meet Holy Cross’ energy needs.
The last unworkable replacement for Holy Cross’s heating system is a waste to energy system. WTE plants burn trash in order to produce heat and/or electricity. Not everybody considers WTE a renewable energy source, but arguments in its favor have strong merit. If trash is not burned in a waste to energy plant, it is typically deposited into a landfill. As the trash decomposes, methane and carbon dioxide are released into the atmosphere, and land that would otherwise provide a habitat for a multitude of species becomes uninhabitable. Furthermore, the gas released from WTE plants is treated to reduce the damage it would do to the environment. So while WTE plants do produce emissions, these emissions are lower than the emissions produced by traditional methods of eliminating trash. WTE would be an attractive option for the College because it would be able to provide 100% of Holy Cross’s heating needs. However, installing a WTE plant would be a daunting undertaking. The initial investment to create such a plant would be massive, and the College would actually need to find an energy source outside of just its waste production in order to properly fuel the WTE plant. In Millbury, MA, just south of Holy Cross, there exists a very large WTE plant that already receives the large majority of the trash produced in the greater Worcester area. In fact, this plant even receives the College’s trash. Thus, finding waste to fuel a Holy Cross WTE plant would require sourcing materials from greater distances and trucking those materials in, which would release carbon into the atmosphere in and of itself. In tandem with the excessive upfront cost of a WTE plant, these deficiencies make WTE an inviable option for Holy Cross.
Given the problems with these various heating sources, GHP provides the optimal solution for Holy Cross. GHP systems are very common in areas like Iceland, which lie on tectonic faults and thus have access to geothermal hot springs. There is a misconception, however, that GHP systems must lie on fault lines in order to be effective. In reality, GHP systems can be installed almost anywhere. The system works by installing a closed loop of piping deep into the ground and pumping water through the system. As the water in the system travels deeper underground, it is heated by the increasing subsurface temperatures of the Earth. This heated water is then utilized to warm buildings. Interestingly enough, GHP systems can also provide cooling needs. In the summer, surface temperatures become hotter than subsurface temperatures, rendering the temperature of the water that is pumped through a GHP system much cooler than the temperature of the outside world. Because of this, GHP is not only capable of providing 100% of the College’s heating needs, it could also provide for the College’s cooling needs. This, in turn, would greatly reduce the amount of electricity that Holy Cross uses. Unfortunately, my partners and I found it impossible to get an accurate cost estimate for installing GHP systems at Holy Cross. GHP systems are installed on a building by building basis, but the College does not track how much heat is sent from the central boiler to each individual building. It is, therefore, impossible to know how much heat each GHP system would need to produce in each building. Generally speaking, though, GHP systems are cost effective. There are large upfront costs to drill into the Earth and install pipes, but maintenance costs are relatively low. This type of system can last for more than 50 years, and the College would reduce its heating cost to $0.00 after implementation. Given this, GHP systems usually have a payback period of 5-10 years.
Given that a GHP system could potentially provide Holy Cross with 100% of its heating and cooling needs—thus eliminating the College’s largest source of emissions—it would be totally irresponsible of the College not to consider implementing such a system. If Holy Cross remains committed to achieving carbon neutrality, it should begin exploring options for installing a GHP system throughout our campus.