By KEVIN PROFT/ecoRI News staff
The Johnston, R.I.,
facility will feature two 2.5-million gallon digestion tanks, which will break
down food scrap anaerobically. (Kevin Proft/ecoRI News photos)
JOHNSTON, R.I. — Rhode Island’s first two anaerobic digesters were
expected to be up and running by now, based on timelines provided by the owners
of each project.
In Johnston, the Blue Sphere Corp., an
Israeli-based company, stated in November 2015 that it expected its facility to
be operational by the beginning of this year. In the Quonset Business Park in
North Kingstown, NEO Energy, a New-Hampshire based company,
initially expected its facility to be operational by the end of 2014.
In May
2015, NEO modified its timeline, saying that it hoped to have the facility
built by the end of 2016.
Currently, Blue Sphere’s project remains under construction; the
Quonset project has yet to break ground.
Anaerobic digesters process food scrap in such a way that it
produces methane, which is burned on-site to create electricity, and a soil
amendment that can be sold to farmers for certain applications.
This disposal
method for food scrap is generally considered more responsible than sending it
to the landfill, where it occupies valuable space and accelerates climate
change via methane emissions.
Opponents of anaerobic digesters say food scrap would be better
used to rehabilitate soil.
Generators will turn the
methane into electricity, and excess heat from the generators will be used to
maintain the proper temperature of the digesters. The black tanks in the
background are the wastewater treatment tanks.
Johnston project
Blue Sphere broke ground on its Johnston facility in May of last
year. When completed, it will accept 250 tons of food scrap daily and generate
3.2 megawatts of electricity. Hansel Tineo, a project manager for Austep,
the Italian-based builder and future operator of the facility, said it will
begin accepting food scrap come springtime and be fully operational by this
summer.
The facility will include at least 11 structures. Waste haulers
will deliver food scrap to a reception building, where automated equipment
sorts out contaminants such as plastic, and pulps the food scrap. Once pulped,
the food scrap moves through a holding tank and into one of two 2.5-million
gallon digestion tanks, where it breaks down anaerobically — without oxygen.
The food scrap will then enter a second, smaller digestion tank,
where it further decomposes. Anaerobic digestion takes between three and four
months, according to Chris Duhamel, vice president at DiPrete
Engineering, the local engineering firm that helped usher the
project through its complicated permitting process.
The methane created during anaerobic digestion will be piped to
on-site generators that burn the gas to create electricity, which gets
distributed to the power grid.
Upon leaving the smaller digestion tank, the
solid and liquid byproducts of the digestion process are separated. The liquids
get treated in a four-tank wastewater treatment system until they are about as
clean or cleaner than residential wastewater.
The liquid will then be
introduced into the Narragansett Bay Authority’s collection system, which will
further treat the wastewater at a downstream treatment plant, according to
Duhamel.
The solid byproducts of the digestion process are dried, then sold
as a fertilizer.
The facility will receive revenue from three sources: a tip fee
charged to waste haulers delivering food scrap; the sale of energy to National
Grid; and the sale of fertilizer.
National Grid has agreed to buy electricity
for a price not to exceed 10 cents per kilowatt-hour for the first year,
followed by annual 2 percent price increases, according to David Graves, a
spokesman for National Grid.
The contract lasts for 15 years, with the
possibility of an extension that must be approved by the state Public Utilities
Commission.
North Kingstown
project
While Blue Sphere’s facility in Johnston nears completion, NEO
Energy’s facility planned for the Quonset Business Park has yet to break
ground, despite the company's initial expectation to have the facility
completed by the end of 2014.
The project remains in the environmental permitting process,
according to Tony Callendrello, chief operating officer for NEO Energy. He
couldn't provide a timeline for how the project will proceed.
The Rhode Island Department of Environmental Management's Office
of Air Resources issued a draft permit to Neo Energy on Feb. 24 for its review
and comment, according to an agency spokeswoman. To date, the department hasn’t
received a response to the draft permit, she said. The Office of Waste
Management issued a putrescible waste composting registration to Neo Energy in
January.
The proposed project would accept about 68 tons of food scrap
daily and generate 500 kilowatts of energy. NEO signed a power-purchase
agreement with National Grid in September 2014.
The utility company agreed to
buy energy from the anaerobic digestion facility for 19.55 cents per
kilowatt-hour. In accordance with state law, the contract will terminate 36
months after its signing — Sept. 5, 2017 — if the facility isn't complete by
then.
Tiverton idea
Blue Sphere, in conjunction with DiPrete Engineering and Austep,
is considering building an anaerobic digester on an 8-acre town-owned parcel in
the industrial park off Progress Road in Tiverton.
The plant would be 1-2
megawatts, according to Mark Rousseau, Tiverton's town planner.
Blue Sphere has provided a letter of intent to the town to buy the
land if it's able to secure the required permits and a power-purchase agreement
with National Grid, according to Rousseau.
A public presentation about the
proposed facility was held at a Town Council meeting last spring and included
representatives from Blue Sphere, DiPrete Engineering and Austep. Rousseau
expects to have more information on the status of the project by June.
The industrial park is already the site of a 265-megawatt natural
gas-fired power plant operated by Tiverton Power.
"I support renewable energy, but I think its going to take a
long time to get ourselves off natural gas," said Rousseau, regarding the
discrepancy in electrical output between the existing fossil-fuel power plant
and the proposed anaerobic digester. "We just have to keep chipping
away."