Page 54 - Energize July 2021

TECHNICAL

Waste to wheels: a closed loop
RNG and its conversion to a fuel source for refuse collectors, as
well as landfill operators, creates a closed-loop system bringing
in revenue as it decreases costs. People pay to have their refuse
collected and taken to the landfill where it is buried. In as little as
six months, the organic matter starts to decompose and produce
methane, which is collected via a series of pipes and undergoes
primary treatment (removing moisture and excess particulate
Figure 2: Benefits for all
matter), secondary treatment (removing contaminants and
compressing to create biogas) and finally a third stage where CO 2,
oxygen, and nitrogen gases, along with volatile organic compounds carbon adjustment, with revenues returned to the public in the form
(VOCs), are removed. The purified RNG is then compressed for use of a dividend check in exchange for elimination and simplification of
in vehicles/equipment onsite – or injected into a natural gas pipeline, greenhouse gas regulations.
producing a revenue stream. CO 2 emissions from the average truck hauling freight in the US is
A refuse/recycling truck can offload at one end of the landfill estimated at between seven and nine tons of CO 2 per year – so for
and refuel for free at the other end. The RNG produced can also be fleets with hundreds or thousands of trucks running 800 km per day,
used to fuel other types of equipment at a landfill from bulldozers to the penalties could be substantial.
dump-to-skid steers or even fuel electric generators. Any piece of For this reason, there’s a great impetus to final alternative
equipment which uses an LNG or CNG engine can use RNG as fuel. technologies, from biofuel and hybrid vehicles to fuel cells and fully
The experience has been eye-opening for Waste Management’s electrified trucks. A carbon tax is an element of the Paris Accord,
Moreno Valley operations, which has had natural gas engines since and the US is one of the last industrialised countries without a
the 1990s. In addition to the fiscal benefits, they cite advantages of carbon tax strategy, with projected prices ranging anywhere from
slow fuel facilities, minimising labour hours, reduced noise and of $41 to $125/t.
course, an enhanced public image, as by-products of this “greener” The writing is on the wall, and the quickest way for fleets and
approach to the industry. For more information, click here. large retailers to avoid future carbon tax penalties with a net-zero
One of the most recent RNG construction projects is carbon impact is by using RNG-fuelled vehicles. The increased
Minnesota’s Inver Grove Heights, where a $40-million plant is demand for RNG will fuel more and more conversion of mid-size
scheduled to be operational by March 2022 and will convert biogas landfills to RNG production based on economics alone.
from its landfill and send it to the Xcel Energy pipeline. The Inver
3
Grove Heights facility processes 170 m /min of landfill gas into RNG Benefits for all
– the equivalent of 200 kl of vehicle fuel per day. To fully appreciate the benefits, consider this: If you were to convert
The RNG produced at this facility qualifies for credits under a fleet of 100 trucks producing 8558 metric tons of CO 2 per year to
the Renewable Fuel Standard law, part of the Energy Policy Act, natural gas use, it would be equivalent to taking 1522 passenger
from 2005. It is anticipated that the company will be able to sell cars off the road, or eliminating the greenhouse gas emissions
customers fuel with a “near zero carbon imprint” at a price less than created by burning 18 500 barrels of oil for electrical generation, or
diesel fuel. the greenhouse gas emissions emitted from heating and powering
942 homes for an entire year.
Pressure is building
While the benefits of transforming an existing landfill to enable RNG Waste not, want not
production are huge from an environmental and financial standpoint, RNG has already surpassed LNG and CNG combined, and it’s a
costs for putting in an engineered liner, plumbing the site with trend which will accelerate in the near future. It utilises scalable,
vertical and horizontal lines, collecting the gas and leachate while proven technology which can have an immediate impact, both by
preventing migration into the air, land or water and then processing lessening methane release into the atmosphere and reducing the
the LFG into methane, are substantial. world’s dependence on fossil fuels. RNG turns waste into wealth,
That’s where national, state and local governments come into creating a better pipeline to a greener, healthier future.
play. On Earth Day 2021, US President Biden announced that the While other promising technologies are on the horizon, RNG is
country was renewing its commitment to the Paris Accord. here now – the ideal combination of positive environmental impact
“Building a clean and equitable energy economy and addressing and sound economic policy, and one that is backed by government,
the climate crisis is a top priority of the Biden Administration… large companies and earth advocates all across the globe.
putting the United States on a path to achieve net-zero emissions, RNG is the perfect marriage of environmental impact with sound
economy-wide, by no later than 2050”, he said. economic policy, backed by large companies and earth advocates
Funding is being made available for research and development alike. n
projects to decarbonise both cars and trucks through the
Department of Energy (DoE), including $61-million for biofuels Reference
research. There is considerable debate on the best methodology to 1. Renewable natural gas plant planned for landfill in Inver Grove
achieve this goal. The Climate Leadership Council (CLC) has invited Heights, StarTribune.com
business leaders from companies, including petrochemical and 2. EPA: Landfill Methane Outreach Program Newsletter – May 2020
automobile makers, and others, to help develop workable proposals
to achieve this goal. Contact Tanya Cairns, Cummins, Tel 011 450-3400,
The CLC is currently proposing a $40/t carbon fee and a border tanya.cairns@cummins.com

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