LONDON, April 6 (Thomson Reuters Foundation) - Since a
Danish wastewater plant produced more energy than it needed last
year becoming a "green power station", engineers from Serbia to
China have been lining up to learn how it has managed to turn
wastewater into a valuable energy source.
Most water treatment plants - that convert wastewater and
sewage into something that can go back into the water cycle -
are energy hogs, with the race on to find technologies to cut
electricity usage to save costs and the environment.
So international interest was piqued when the Marselisborg
Wastewater Treatment Plant in Aarhus, Denmark's second largest
city, generated nearly 70 percent more energy than it needed in
2016 following a 3 million euro ($3.2 million) upgrade.
This put Aarhus on track to become the first city in the
world to provide and pump fresh water to all its citizens from
energy created solely from household wastewater and sewage,
escalating interest in how to make wastewater into a resource.
"We are only using the potential of wastewater," Per
Overgaard Pedersen, a chief engineer at Aarhus Vand, the water
company that runs Marselisborg, told the Thomson Reuters
Foundation in a phone interview.
"We're not using heat pumps, wind mills ... like many other
The Marselisborg plant says it became energy self-sufficient
by extracting carbon from wastewater and sludge and pumping it
into digesters with bacteria to produce biogas, mostly methane,
that is burned to make heat and electricity.
While the process is not new, the success rate is, with
Marselisborg putting this down to investing in new technologies
and tailored equipment to stops leaks and cut maintenance costs.
Pedersen said investment in new technologies between 2003
and 2016 helped the Marselisborg plant reduce its power
consumption by 33 percent.
"It's quite important for a utility like us," he said.
Marselisborg is being heralded as an example and attracting
international attention as the attitude towards wastewater
The Paris-based International Energy Agency in its "World
Energy Outlook 2016" singled out Marselisborg as an example of
how wastewater treatment can be energy neutral in the future.
The United Nations, in a 2017 World Water Development Report
last month, said wastewater shouldn't be seen as a problem but
rather as a valuable resource which could help meet the demands
for water, energy and nutrients.
Energy efficiency is important for utilities like Aarhus
Vand because it can cut costs and aid the environment.
The U.S. Environmental Protection Agency (EPA) says
electricity accounts for 25 to 40 percent of water utilities'
budgets, while the machinery running all day can be one of the
biggest contributors to greenhouse gas emissions in a community.
Marselisborg, which annually treats more than 30 million
cubic metres of wastewater from its 300,000 customers, uses the
energy it generates to run sewer pumps and to pump clean water
to its customers.
Excess heat and power - the equivalent of energy consumption
of 500 households - is being sold to the local grid, providing
The plant produces 2.5 gigawatt (GW) of heat per year that
it feeds into the local district heating system, which -
combined with the surplus electricity - equals 99 percent of
total energy needed for wastewater treatment and water supply.
"Taking that into consideration has made it possible to
reduce our operational cost by approximately 3 to 4 percent,"
Although visitors from countries as far-flung as South
Africa have come to learn from Marselisborg experience, Pedersen
said adapting the plant's model might not work for everyone,
especially smaller plants with less consumers.
"It's going to be difficult because for a smaller plant it
will probably be too expensive to do the investment in the
digesters," he said.
"In our context here in Denmark I think 100,000 persons
would be a good guess (for the investment to be feasible) but it
simply depends on what facilities you have in the plant and the
($1 = 0.9371 euros)
(Reporting by Magdalena Mis @magdalenamis1, Editing by Belinda
Goldsmith; Please credit the Thomson Reuters Foundation, the
charitable arm of Thomson Reuters, that covers humanitarian
news, women's rights, trafficking, property rights, climate
change and resilience. Visit news.trust.org)