The Efficiency of Natural Gas Versus Electricity

On average, a house fueled by natural gas is responsible for about one-third fewer greenhouse gas (GHG) emissions than a comparable all-electric home.

Why? Let’s take a look at what’s called the full fuel cycle, which accounts for how much energy is retained – or lost – from an energy source until its final use in your water heater, oven, or home heating system. With the full fuel cycle in mind, natural gas’s direct use comes out as a winner in the energy efficiency race. For example, by the time you turn on an electric appliance, up to 68 percent of the original fuel’s energy value has been lost. That means the full fuel cycle efficiency is about 32 percent. By contrast, a natural gas appliance’s full fuel cycle efficiency is about 92 percent – a substantial difference. More efficient use of fuel means less energy loss and less that needs to be produced, which reduces GHG emissions.

The graphic illustrates the efficiency of natural gas and electricity on a full fuel cycle basis for 100MMbtu (100 million British Thermal Units). A Btu is a measure of the energy content in fuel expressed by the heat required to raise the temperature of one pound of water by one degree Fahrenheit at a specific temperature and pressure. One Btu equals 252 calories, 778 footpounds, 1,055 joules, or 0.293 watt-hours. One cubic foot of natural gas contains about 1,027 Btus.

Renewable is Doable

 

Renewable is Doable

By Alex Schay

In North America, we rely on natural gas to provide the majority of our space and process heat. It is also safe to assert that, in most cases, the next MegaWatt hour will be generated through the combustion of natural gas. For example, 80% of the heat used for food processing is derived from natural gas.

In order to make meaningful progress toward addressing climate change, gas utilities are taking steps to reduce the carbon footprint of their fuel mix. Gas utilities have five tools that will enable them to reduce the carbon intensity of their fuel, including:

  • Energy efficiency;
  • Reduce gas flaring and fugitive methane emissions;
  • Tighten up pipeline infrastructure to minimize methane leakage;
  • Surplus renewable electricity may be used to convert water into Renewable Hydrogen (RH2); and,
  • Decomposition of organic waste may be used to produce Renewable Natural Gas (RNG), e.g., at landfills, at commercial & municipal wastewater treatment plants, as well as on dairies and confined animal feeding operations.

What is Renewable Natural Gas?

Both Conventional Natural Gas and Renewable Natural Gas (RNG) contain an identical CH4 molecule. RNG is a green fuel that comes from waste material, such as garbage, human waste, and animal manure. As such, RNG uses waste streams that are part of the current lifecycle to create a useful product that burns cleanly and significantly reduces Greenhouse Gas emissions as compared with gasoline or Diesel.

 

GHG reductions accrue when using CNG and RNG as opposed to gasoline or Diesel
Conventional (fossil) Natural Gas (CNG) 5% – 15%
Renewable Natural Gas (RNG) sourced from a landfill 40% – 50%
RNG sourced from a municipal wastewater treatment plant 75% – 85%
RNG generated from animal manure Ø  > than 100%

Food processing plants may offer a special opportunity for the production of RNG. Many food-processing facilities have their own wastewater treatment plant (WWTP). Often times, gas generated at commercial WWTPs is captured in covered lagoons and then sent to a flare. These types of waste-management scenarios offer significant opportunities to improve the gas collection, production, and utilization.

Because the Federal Renewable Fuel Standard classifies biogas generated at food-processing facilities as an “Advanced Biofuel,” RNG generated at such projects will only earn D5 Renewable Identification Numbers (RINs) when used as a transportation fuel. More valuable D3 RINs, however, are generated at landfills, municipal WWTPs, as well, as from animal manure. As such, RNG from food-processing facilities will not deliver as much economic benefit as RNG from landfills or municipal WWTPs when used as a transportation fuel.

To that end, RNG produced at food-processing plants may offer a cost-competitive resource that gas utilities may use to reduce their fuel mix’s carbon footprint. For example, a recent analysis of anthropogenic GHG emissions associated with RNG that will be produced at a dairy-processing plant in Washington State revealed that this fuel will have a carbon footprint that is more than 95% lower than conventional natural gas. In this way, food processors may help gas utilities reduce their fuel mix’s carbon intensity in a cost-effective manner.

At present, 32% of US energy consumption is fueled by natural gas. Unlike electricity, which must be used immediately or lost forever, RNG and RH2 can be stored for use when needed. A diversified decarbonization strategy will embrace all technologies, including cleaning up both the electricity grid and natural gas pipeline network. With this context in mind, we encourage an “All-of-the-Above” strategy as we work to decarbonize our energy future.