Greenhouse Gas Management of Fossil Fuels

Most hospitals use combustion to convert various fossil fuels — usually methane, propane and diesel fuel — into other forms of energy, primarily heat and electricity. Heat generation serves three kinds of needs: certain end-use process loads, domestic hot water heating and space heating, including reheat.

End uses include humidification, cooking, cart wash, humidification and sterilization. Combustion for electrical energy generation includes both on-site normal power generation and emergency generation.  

Consumption of fossil fuels is very climate dependent. The engineering firm Grumman Butkus maintains a benchmarking database1 which summarizes the energy use of 132 hospitals. This analysis shows that fossil fuels in the Midwest on average represent approximately 60% of a hospital’s energy consumption, compared to 40% electricity. An analysis2 of Local Law 84 benchmarking data, published by New York City, shows a fuel mix of 70% fossil fuels and 30% electric energy. On the other hand, in a mild-dry climate such as that found in most of California, the fuel mix for hospitals is closer to 45% fossil fuels and 55% electric.  

The Midwest and northeastern United States have cold, wet winters, which drives significant fossil fuel consumption. In densely populated cities where the electric grid is heavily taxed during periods of peak loads, hospitals have been historically encouraged by state and utility incentive programs to invest in co-generation systems and gas- or steam-fired chillers. These factors make reducing emissions related to fossil fuels significantly easier for hospitals located in warmer climates and rural areas.  

How to measure and report:

The most straightforward means of measuring emissions related to fossil fuel consumption is by tracking fossil fuel purchases and applying multiplying the volume of fuels purchased by a fuel-specific greenhouse gas emissions factor. The Environmental Protection Agency (EPA) has published a very comprehensive list of emissions factors which can be found on the EPA’s website3.

Note that the EPA factors are given in kilogram (kg) of emissions per million British thermal units (MMBtu) and most emissions reporting standards utilize metric tons for tracking. Converting kg per MMBtu to metric ton (MTon) per MMBtu requires further multiplying the EPA factors by a conversion factor of 0.001 MTon/kg.

Another easier method is to simply enter energy consumption into the ENERGY STAR® Portfolio Manager tool, which will provide an estimate of greenhouse emissions.  

Accurately reporting fossil fuel emissions can be significantly more complex. Beyond combustion, there are Scope 3 emissions associated with consumption of these fuels. Fuel oil includes emissions from recovering and processing the fuel oil all the way to the emissions associated with the truck which delivers the oil to the hospital. Gaseous fuels, such as natural gas and propane, similarly have Scope 3 emissions associated with the recovery and pipeline transport of these fuels. For gaseous fuels, these Scope 3 emissions are much easier to track, as utility companies publish loss factors (typically in the 2% to 5% range for natural gas), which are often included as a line item on the hospital’s invoice. Unburned methane from leakage is a greenhouse gas in its own right; according to the European Union, the global warming potential of unburned methane is 28 times higher than that of carbon dioxide over a 100-year time scale4

How to manage: 

Hospitals have three basic ways to manage the bulk of fossil fuel emissions. First, they can deploy a wide range of energy efficiency strategies that will reduce both the emissions and the financial resources associated with combusting these fuels. Second, they can electrify the processes that use combustion to generate various forms of heat and other energy. Finally, they can swap fossil fuels for various renewable forms of methane. 

Much material from American Society for Health Care Engineering (ASHE)5, ASHRAE6, and the California Energy Commission7 is available that well define ways to reduce energy consumption. This guide is not intended to restate all this information, but the reader is urged to refer to these important resources, and to make use of them. Many local utility companies offer technical assistance and financial incentives to help hospitals to deploy various energy reduction strategies. 

One seemingly attractive efficiency opportunity is cogeneration. This system takes the heat from electricity production and uses it to avoid additional on-site combustion. Co-generation and gas- or steam-fired chillers may increase local emissions by burning gas on-site but displace significant amounts of emissions from upstream thermal generators that are, in most cases, less efficient and emitting more greenhouse gases — particularly during periods of high electric demand, when distribution losses are high due to grid congestion and oil-fired or coal peaked generators may be ramped up. 

There is not a single electric grid in the United States that is 100% carbon-free, and even in the cleanest grids, there is a significant amount of time when co-generation systems are displacing dirtier fossil generators. Determining what generators a co-generation system is displacing is very time- and location-dependent, making it very difficult to track. However, for those endeavoring to try, the EPA has developed calculators and methods for determining the emissions reductions associated with these systems. Among the easiest to use can be found here, which allows the co-generation system owner to estimate the carbon emission displaced by their specific co-generation system.

A significant challenge with co-generation systems, though, is that they are likely to become stranded assets as the grid continues to decarbonize. As prices of renewable energy sources continue to fall — and as they become increasingly prevalent, especially combined with long duration energy storage systems — investments in new fossil fuel combustion plants, even those that are highly efficient due to capture of waste heat, are likely to become obsolete. 

Electrification is becoming an increasingly prevalent and crucial important decarbonization strategy. Most loads in most hospitals can be readily retrofitted with electric power. Such conversion may require upgrades to electrical system capacities, especially emergency power systems where codes require backup for specific uses, such as patient room heating. Often, these impacts can be managed, as current practice of electrical engineering tends to result in oversized electrical systems relative to actual load. Grids across the country are increasingly becoming less carbon intensive, and will continue to do so, such that conversion of natural gas combustion to electrification is the best long-run strategy for decarbonization. In addition, hospitals have increasing options for securing renewable electrical supply, which can accelerate this progress. 

Finally, methane can be derived from what are defined as “renewable” sources. These include landfill waste gas and livestock manure.8 These losses can work both ways; methane is generated naturally through the decay of organic material. There are numerous sources of naturally occurring methane that will be extremely difficult to eliminate — for example, from farms or sewage treatment plants. If not put to productive use, these sources of methane would be vented to atmosphere or flared (burned without making productive use of the heat). 

Some sources of naturally occurring methane are injecting methane into the natural gas pipelines and offering renewable gas credits, (which function similar to renewable energy credits) in the electric markets. Purchase of these credits is meant to encourage the further development of the infrastructure to recover methane from recurrent sources of generation. In turn, the hospitals could claim an emissions reduction by making use of gas that might otherwise be vented in a more potent form (methane vs. carbon dioxide) or simply flared (which produces carbon dioxide). Hospitals should tread carefully when purchasing these types of offsets; the market is not well regulated in some areas of the country, and the provenance and effectiveness of these renewable energy and renewable gas markets is debatable. 

Other liquid fuel such as fuel oil or diesel may be partially or fully biogas. These fuels may use cooking oil waste product from restaurants, reprocessing it into diesel or fuel oil. However, the overwhelming source of these fuels is agriculture — for example, turning corn into diesel or fuel oil. In some areas of the country, there are requirements that a percentage of fuel is biogas. In New York, for example, there is a requirement that all heating oil contain 5% biodiesel, increasing to 10% by 2025 and 20% biodiesel by 2030. While these biofuels ostensibly reduce emissions, as they are renewable (i.e., one can grow more corn), they often do not account for the Scope 2 embodied emissions related to the agricultural inputs required to grow the biofuel feedstock and process that feedstock into a fuel. These biofuel requirements may increase emissions.  

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