Operational Energy Use WBLCA stage 6 Question

We have a question about best practice in building our WBLCA stage B6 for a university campus building. The campus buys energy from the state grid, SG Carbon Factor (SGCF), it purchases RECs for ±70% of electrical energy demand (REC), and provides for campus heating with an a steam plant, campus steam plant carbon factor (CSPCF). Does this look right as a formula?:

[(Annual electricity demand X - RECs) * SGCF] + [Annual heating demand X * CSPCF]

As an added complexity, we will also try to model a linear decarbonization rate for the SGCF, which we will reference the States goals for their eGrid decarbonization, and a stepped decarbonization for the CSPCF given that the existing natural gas plant is scheduled to be converted to landfill gas and/or biomass, which is abundantly available as a local manufacturing waste product.

We’ve been using the EPAs Emission Factors for GHG inventories to determine the emissions factor for steam production, which Table 7 indicates a CO2 factor of 66.33 kg/MMBtu for steam and heat.

For the eGrid carbon factors, we have been referencing the EPAs data explorer to narrow in on the States emission factors.

Any help confirming the above is much appreciated.

I have a few thoughts on this:

  • The consideration of RECs is certainly controversial, and subject to some interpretation. In my opinion, you can only consider RECs to be a direct offset like this if you can ensure that they are local and benefitting the grid that you are consuming electricity from. If your local grid is relatively dirty, and your purchased RECs are supporting a local project that reduces emissions on that local grid grid, then I think this calculation method is valid. If you are purchasing RECs that support a project in a different region that does not directly support your local grid, then it depends (this would potentially not be a valid way to calculate consumption, depending on who you ask). This also does not get into the whole notion of how grid emissions vary over the course of a day.
  • If you are comfortable with the source of your RECs (and that they are reducing emissions on the grid that your university is connected to), then yes, this calculation for electricity would work as an estimate of electricity emissions
  • Are there any additional natural gas or other fuel loads to consider? I would expect that some university buildings use natural gas either because they are not connected to the steam plant or because they have other process loads
  • For decarbonization over time, I would consider using NREL’s Cambium data, which provides grid emission factor rates projected to 2050 (assuming emissions reductions)
  • For steam, I’ll give you the frustrating answer of ‘it depends’ - If the EPA emission factor assumes the same method of steam production (e.g., natural gas-fueled vs. coal vs. …), then this would serve as a valid high-level estimate, though it wouldn’t take into account the efficiency of your steam plant. The best estimate for a steam emission factor would be from measuring the fuel consumption of your heating plant and multiplying that by the appropriate fuel emission factor (e.g., natural gas, coal, …) rather than applying the factor for steam heat, which doesn’t take your university’s unique conditions into account.

I hope this is helpful!


P.S. I spent 10 years as an energy engineer, performing energy audits, modeling, analysis, and design review on a large number of projects, including some university and district-level projects.


Some additional thoughts on RECs, which as Matt said are contentious:
RECS and power are sold separately, meaning that the REC is sold in addition to the power being sold. My understanding is that RECS were originally to provide the cost delta between legacy power generation like fossil fuels and renewable power generation, which used to cost more. Since renewables are now the cheapest form of energy generation (there is no fuel cost) in most of the US and world, what are RECs? One point of view is that they are meaningless because the cost delta is now below zero (costs of developing and operating legacy power plants are high that the costs of renewables). Another point of view is that they provide an additional income source for renewable energy generators making the transition to renewable energy more rapid. In any case, a carbon neutrality claim should be based on all-electric (efficient!) design having 100% renewable energy that includes a long term energy purchase that includes and retires RECs, but is not just RECs. Energy purchases should include new generation dedicated to a given project, not reallocation of existing generation, and be additional to any RPS energy standard that a utility has. My opinions only, of course.


We added tiers to LEED v4.1 and draft v5. Initially we made 5 tiers to v4.1 for levels of RECs, green power purchases, on-site vs off-site. We heard those were too cumbersome so we went back to 3 Tiers but the hope was to push more construction of new renewables so we give more credit towards these RECs than legacy RECs.

Tier 2: New off-site renewable energy
o Off-site renewable electricity that is produced by a generation asset(s) built within the last five years or contracted to be operational within two years of building occupancy.
o Green-e Energy certification or equivalent is required for one-time purchase and delivery of EACs of more than 100% of the project’s annual electricity use.

Keep in mind that procuring RECs does not decrease the site’s electricity use; it modifies the environmental impacts associated with the electricity use.

Within the LCA, you may want to consider keeping the electricity use the same but creating separate characterization factors associated with the portion of electricity covered by the RECs. Not all RECs have zero emissions. You should use the emission factors associated with the RECs that were procured.