Consultants: Using landfill for power, heat would cost city too much money

It seemed like a good idea to tap the gas at the old Grand Forks landfill for generating power and heat, saving the city money, but consultants told the City Council's service committee today that it'll probably cost more money.

Depending on the configuration of the power system, the city could be in the hole by $3.1 million to $3.7 million over the next 20 years.

The city landfill just isn't big enough to generate the amount of gas needed, said Scott Martin, an engineer with Burns & McDonnell, the Kansas City, Mo., firm that designed the new landfill.

"These projects are strictly economy of scale driven," he said. The Fargo landfill has a profitable gas-power generation system, he said, but it's roughly twice the size of the Grand Forks landfill.

By his estimate, Grand Forks could collect 209 cubic feet of gas per minute in 2010, an amount that would drop to 104 cfm by 2030 -- old garbage doesn't generate much gas. Yet a minimum of 450 cfm on average over the life of the landfill is needed to run a 1.5-megawatt generator, which is the minimum needed for financial viability.

Committee members, after asking a few questions, agreed to just file the consultant's report and leave it at that for now.

Less promising

A 2008 initial estimate by UND's Energy and Environmental Research Center had raised some hopes that the project was doable. Using formulas rather than drilling for samples, which costs more money, the EERC thought there might be enough gas to power a 2-megawatt generator for 20 years.

It also thought a gas-power generation system would cost $3.5 million and electricity rates were such that a return on investment was possible within six years.

That led to a more detailed study by Burns & McDonnell, paid for with $75,000 in federal and state grants.

The firm found it would take 700 cfm of gas to power a 2-megawatt generator and, while there is there is more than that in the landfill in the beginning, a lot of it cannot be collected efficiently.

Martin said a minimum of 20 feet of garbage is needed for gas wells to work, and there are several areas in the Grand Forks landfill where that threshold isn't met.

Yet, the smaller network of wells and pipes would still cost $3 million to build. With a heating system alone, the total cost of the project would go up to $4.5 million. With a power generator it goes up to $5.7 million.

Another project

Martin did raise one potential power generation project aimed at the new landfill. If it could be converted to what's known as a bioreactor, it could generate enough gas over its decades-long lifespan and save money.

A bioreactor is essentially a landfill with water in it, encouraging microbial growth and increasing the gas they generate. Fresh garbage makes for more gas than old garbage so the city could make almost immediate use of the system.

But, Martin said, it costs a lot more to build and operate than a regular gas-power generation system.

Reach Tran at (701) 780-1248; (800) 477-6572, ext. 248; or send e-mail to ttran@gfherald.com .