The term net zero describes processes or entities that either have no net greenhouse gas emissions (often called net zero carbon, net zero emissions, or carbon neutral) or no net energy consumption (sometimes called net zero energy).
Net zero carbon
Net zero emissions describes a circumstance where an entity has an overall balance between greenhouse gas emissions produced and greenhouse gas emissions taken out of the atmosphere. Achieving net zero carbon is generally a two-step process:
- Reduce carbon emissions as much as possible, which is typically achieved by reducing energy consumption through implementation of energy efficiency measures coupled with a commitment to utilize renewable or other zero carbon energy sources. In the future, this may also include implementing carbon capture technologies in the organization’s processes.
- For remaining emissions, funding projects by other entities that reduce an equivalent amount of carbon emissions or remove an equivalent amount of carbon from the atmosphere. The method for funding is often a carbon offset, which is a tradeable instrument whereby an entity implements strategies that reduce greenhouse gas emissions and a third-party organization certifies that emissions have been reduced. The certification organization then issues offsets that can be sold to entities attempting to achieve net zero carbon emissions.
Net zero energy
Net zero energy means that a structure (a home, office building, etc.) produces at least as much energy as it consumes. There are two steps to accomplishing this goal:
- Incorporate as much energy efficiency into the building as possible so that the energy needed to attain expected comfort levels is as low as possible.
- Incorporate distributed generation so that the building produces energy as well as consuming it.
Since building energy consumption is the largest end-use energy sector, the concept of net zero has the potential to reduce energy consumption related to environmental impacts including reducing greenhouse gas emissions. Strategies for moving toward net-zero building include:
- High levels of insulation
- Energy-efficient appliances and lighting (which not only reduce primary electricity consumption but also reduce waste heat and the need for space cooling)
- Efficient heating, ventilating, and air conditioning systems (including consideration of geothermal heating and cooling)
- Use of natural lighting, natural ventilation, and passive solar heating
- Use of self-generation including solar photovoltaic and/or combined heat-and-power systems
- Use of battery or thermal storage
- Design techniques such as integrated design and life cycle environmental analysis
Numerous net zero residential and commercial buildings have been constructed and had their performance verified. It will take time and many more successful projects before net zero buildings can prove themselves as the prevailing paradigm. But continued research and the knowledge gained from these projects opens the door for the potential of dramatically lower net energy usage in the future. The Rocky Mountain Institute suggests by 2050 the average building could use one-half to three-quarters less energy than today. What impact might this have on the overall energy picture? Studies show that over 40% of the energy consumed in the U.S. is consumed by residential and commercial buildings. So, if net zero allows us to reduce demand by 50%, we would drop our energy consumption by 20%. This scenario introduces a whole new concept: economic growth coupled with reductions in energy usage.