Natural gas will play a leading role in reducing greenhouse-gas emissions over the next several decades, largely by replacing older, inefficient coal plants with highly efficient combined-cycle gas generation. Thats the conclusion reached by a comprehensive study of the future of natural gas conducted by an MIT study group comprised of 30 MIT faculty members, researchers and graduate students.
The two-year study, managed by the MIT Energy Initiative (MITEI), examined the scale of US natural gas reserves and the potential of this fuel to reduce greenhouse-gas emissions. The report examines the future of natural gas through 2050 from the perspectives of technology, economics, politics, national security and the environment.
The report includes a set of specific proposals for legislative and regulatory policies, as well as recommendations for actions that the energy industry can pursue on its own, to maximize the fuels impact on mitigating greenhouse gas. The study also examined ways to control the environmental impacts that could result from a significant expansion in the production and use of natural gasespecially in electric power production.
The study found that there are significant global supplies of conventional gas. How much of this gas gets produced and used, and the extent of its impact on greenhouse gas reductions, depends critically on some key political and regulatory decisions.
Key findings. The US has a significant natural gas resource base, enough to equal about 92 years worth at present domestic consumption rates. Much of this is from unconventional sources, including gas shales. Globally, baseline estimates show that recoverable gas resources probably amount to 16,200 trillion cf, enough to last over 160 years at current global consumption rates. In the US, unconventional gas resources are rapidly overtaking conventional resources as the primary source of gas production. The US currently consumes around 22 trillion cf per year and has a gas resource base now thought to exceed 2,000 trillion cf.
In order to bring about the kind of significant expansion in the use of natural gas identified in this study, substantial additions to the existing processing, delivery and storage facilities will be required in order to handle greater amounts and the changing patterns of distribution (such as the delivery of gas from newly developed sources in the Midwest and Northeast).
Environmental issues associated with producing unconventional gas resources are manageable but challenging. Risks include: shallow freshwater aquifer contamination with fracture fluids; surface water contamination by returned fracture fluids; and surface and local community disturbance, due to drilling and fracturing activities.
Natural-gas consumption will increase dramatically and will largely displace coal in the power generation sector by 2050 (the time horizon of the study) under a modeling scenario where, through carbon emissions pricing, industrialized nations reduce CO2 emissions by 50% by 2050, and large emerging economies, e.g. China, India and Brazil reduce CO2 emissions by 50 percent by 2070. This assumes incremental reductions in the current price structures of the alternatives, including renewables, nuclear and carbon capture and sequestration.
The overbuilding of natural gas combined cycle (NGCC) plants starting in the mid-1990s presents a significant opportunity for near term reductions in CO2 emissions from the power sector. The current fleet of NGCC units has an average capacity factor of 41%, relative to a design capacity factor of up to 85%. However, with no carbon constraints, coal generation is generally dispatched to meet demand before NGCC generation because of its lower fuel price.
Modeling of the ERCOT region (largely Texas) suggests that CO2 emissions could be reduced by as much as 22% with no additional capital investment and without impacting system reliability by requiring a dispatch order that favors NGCC generation over inefficient coal generation; preliminary modeling suggests that nationwide CO2 emissions would be reduced by over 10%. At the same time, this would also reduce air pollutants such as oxides of sulfur and nitrogen. HP