Hunton Energy to build synthetic natural gas plant at Dow chemical facility; biomass as feedstock, CO2 captured and stored

In a very interesting development that shows the versatility of biomass, Hunton Energy and the Dow Chemical Company have signed a Memorandum of Understanding (MOU) that will result in Hunton Energy building and operating a Synthetic Natural Gas (SNG) plant partly fed by biomass at Dow’s Oyster Creek Facility on the Texas Gulf Coast. Under the proposed 15-year agreement with Dow, the Hunton Energy facility is slated to produce SNG and will use steam turbines to produce additional power from its byproduct steam. Processes in Hunton’s gasification system will capture 100% of the CO2 emissions from the facility for use in enhanced oil recovery and utilize all other byproducts commercially.

Contrary to biomethane which is obtained from the fermentation of biomass into biogas that is upgraded to natural gas quality, SNG is obtained from the gasifiction of carbonaceous feedstocks. When biomass is used as the sole feed, 'renewable SNG' is obtained, called 'green gas' [*.pdf] or 'bio-SNG'[*.pdf] in Europe, to distinguish it from biogas. Interestingly, the carbon dioxide that is generated from gasification can be captured and stored, or used commercially. When SNG is made from a pure biomass feedstock, a fuel with an ultra-low carbon dioxide profile is obtained.

Hunton announces it will indeed utilize biomass such as wood chips and rice hulls besides petroleum coke slurry. These sources are fed along with compressed oxygen into a gasifier. The feed is converted into a high-temperature, high-pressure syngas consisting of CO, H2, H2S, and CO2. The syngas then passes through an acid gas removal process where CO2 and H2S are separated and captured. The H2S is converted to elemental sulfur and sold as a byproduct from the facility. The CO2 is compressed and fed into oil wells in the region for enhanced oil recovery (EOR):
energy :: sustainability :: biomass :: bioenergy :: biofuels :: natural gas :: gasification :: synthetic natural gas :: bio-SNG :: green gas :: biohydrogen :: carbon capture and storage :: enhanced oil recovery ::

After the removal of CO2 and H2S, syngas then passes through a methanation block where it is converted into a synthetic natural gas (SNG) of pipeline quality. Any inorganic materials, such as metals that naturally occur in the feed, are melted by the heat of the reactor.

The hot gas and the molten minerals travel from the reactor into a radiant cooler. The radiant cooler uses the high-temperature heat of the reactants to generate high-pressure steam. The steam will be sold to Dow Chemical Company located next to the gasification facility. Dow will use this steam in their chemical processes instead of burning natural gas to generate the steam. Utilizing the process heat increases the efficiency of the gasification facility and reduces emissions from the Dow plant.

Vaporized water in the gas is condensed, and the molten minerals solidify into slag as the gas cools. The byproduct slag will be sold into the concrete/aggregate market. Water recovered from the process is used to make the feed slurry. The water contains unconverted carbon from the process (schematic, click to enlarge).

Hunton Energy estimates a fourth quarter 2008 groundbreaking for the project.

Route to radical biohydrogen
Note that a similar gasification process can be used in the future to obtain a truly carbon-negative fuel, namely biohydrogen. The methanation step would be skipped and replaced by a shift reactor that combines the CO and H2O from the syngas to generate pure H2 and CO2 (schematic, click to enlarge). As in the bio-SNG process, the CO2 from gasified biomass can then be captured and stored, with the result that a radically decarbonized fuel can be produced: biohydrogen.

The peculiarity of such a carbon negative fuel is that, each time you use it (in a fuel cell or to generate large scale power and heat), you take historic CO2 emissions out of the atmosphere. Most people are have difficulty understanding this strange idea - 'negative emissions' energy has not yet penetrated the green consciousness, because they are so radical. All other electricity sources are carbon-neutral at best, that is, they do not add new emissions to the atmosphere. But they do not take existing emissions out of it. Carbon negative bio-based hydrogen does. Which makes it a most radical weapon in the fight against climate change.

More on the competitiveness of gasification based biohydrogen with the potential to capture CO2 can be found in this recent presentation to the European Parliament [*.pdf].

On a different note, a recent study of more than 20 different future hydrogen production and utilization pathways for transport, indicates biohydrogen from gasification is both the most efficient as well as the greenest production pathway on a well-to-wheel basis. It beats all other techniques which are based on natural gas and coal, or on the electrolysis of water using electricity from fossil fuels, nuclear or renewables like wind (more here).

Huntington's gasification process is the first large scale demonstration of the production of SNG, which opens the future for entirely green SNG and later carbon negative biohydrogen.

References:
Dow: Dow Signs MOU for Gasification Facility Hunton Energy to supply Dow with synthetic gas and steam in Texas [*.pdf] - December 13, 2007.

Hunton Energy: Clean Energy SNG Plant slated for Dow Chemical Facility - Hunton Energy locates innovative gasification plant in Texas - December 13, 2007.

Dr. ir. Harold Boerrigter, "Green Gas (SNG) in the Dutch Energy Infrastructure Potential & Implementation" [*.pdf], Energy research Centre of the Netherlands (ECN) - ECN Biomass, Coal & Environmental research, March 30, 2007.

M. Mozaffarian, R.W.R. Zwart, H. Boerrigter, E.P. Deurwaarder, S.R.A. Kersten, " 'Green Gas' as SNG (Synthetic Natural Gas), a renewable fuel with conventional quality" [*.pdf], Bio-SNG, Contribution to the “Science in Thermal and Chemical Biomass Conversion” Conference, 30 August – 2 September 2004, Victoria, Vancouver Island, BC, Canada.

Biowasserstoff: The Green Hydrogen Economy now [*.pdf] - Presentation at the European Parliament, Brussels - January 10, 2007

Biopact: Hydrogen out, compressed biogas in - October 01, 2006