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NRRI Cultivates a Renewable Energy Future

November 1, 2015

Solar and wind energy readily come to mind when talk turns to alternative energy options. 

But the renewable energy options are much broader – and more complex.NRRI is leading exciting developments in some of the lesser known renewable or alternative energy options, with the potential for significant impact. And yes, solar and wind technologies are part of the portfolio, even if the sun isn’t shining or the wind isn’t blowing. NRRI is looking at innovative energy storage options to balance supply and demand.But what Minnesota might lack in sunshine or steady breezes, it makes up in biomass – wood, forest harvest residues and agricultural byproduct.  How can we get the most BTUs out of those resources?There’s a lot of work ahead and NRRI is working with industry partners Minnesota Power, Xcel Energy, SynGas Technology LLC and the Coalition for Sustainable Rail to get it done.

An old storage building at NRRI’s lab in Coleraine, Minn., has been transformed this summer into a state-of-the-art Renewable Energy Center. This $2.5 million project will enhance the understanding of a variety of processes – characterizing their efficiency, industry applications and environmental impact –on commercially-relevant scales. Technologies are in place to convert woody biomass and agricultural byproducts into renewable, regional fuel products that can be used in combination with coal, diesel and propane. These biomass-based fuels have the potential to reduce sulfur, mercury and nitrogen oxide emissions.

This large-scale demonstration capability will make NRRI the upper Midwest’s go-to research facility for developing alternative energy resources.

Energy research programs underway

Converting biomass to fuels

Solid fuels

  • Torrefaction - This roasting process converts biomass into a solid fuel with properties similar to coal in combustibility and BTU output. The torrefied biomass can be burned with conventional coal in power generation plants to reduce emissions. NRRI is installing an indirect-fired rotary kiln torrefaction and briquetting process that will produce 12 tons of biofuel a day, using wood chips and other biomass as feedstock. A steam-electric boiler/generator system will run in parallel to the kiln producing 100 kilowatts per day from a moving bed torrefaction system which will produce three tons of solid biofuels a day.
  • Hydrothermally modified birch bark for biofuel binder – Once biomass has been torrefied, it must be consolidated for ease of transport and to use it as a coal replacement. A binding material is needed to get the modified biomass to hold together as pellets or briquettes. NRRI is applying innovative chemistry to an age-old process to make birch bark tar, similar to that used by Native Americans to seal joints on birch bark canoes. This material can be developed for use as a moisture proof, high BTU, non-toxic and easy-to-use biofuel binder, especially for biomass feedstock that is hard to bind.
  • Hydrothermal Carbonization – A “wet” torrefaction process that captures 100 percent of the carbon in the biomass to produce a biochar slurry material. This material will also be tested as a binder material.

Liquid Fuels

  • Ethanol from hybrid poplar – NRRI is working with a team in the Ukraine to conduct a trial planting of NRRI’s fast-growing hybrid poplars to help this country gain energy independence with biofuels.
  • Syngas (or synthesis gas) production with ilmenite catalysts – A low cost process that efficiently converts biomass-based, low hydrogen syngas into hydrocarbon liquid fuels.

Renewable Energy Resources

Energy Crops

  • Resource Assessment – Minnesota currently harvests about half of its available, sustainable wood supply. There is also an estimated three million tons of roundwood (tops of trees not sawn) and harvest residues along with approximately seven million tons of agricultural biomass available for renewable energy. NRRI is studying the balance of energy needs with increasing forest productivity.
  • Hybrid Poplar – NRRI’s hybrid breeding program has produced genetically improved trees that can provide quick-growing energy crops on marginally productive lands. The Cottonwood/Black Poplar genus developed at NRRI grows to harvest size in eight years.
  • Forest Thinning and Productivity Research – NRRI has an ongoing program to optimize yields of aspen and red pine resources by thinning low yield stands and understanding future opportunities.


NRRI is evaluating three 10-kilowatt photovoltaic solar panel installations manufactured by three different companies to test their performance in a northeast Minnesota climate (including cloudy, rainy and snowy days), compare actual data to computer-model data and validate vendor claims. The panels are being tested on the rooftop of a seven-story building in downtown Duluth to understand the variabilities in panel placement and installation.


NRRI is collaborating with other University units and with private industry to determine issues associated with large scale and smaller scale wind power technologies.

  • NRRI helped identify a five-kilowatt gearless turbine for the UMD campus that is being used for power generation and student education projects. Students can monitor the performance of the new turbine under a variety wind conditions and atmospheric conditions.
  • Two energy storage projects are underway. One is a collaborative effort to develop “Pumped Hydro” storage capabilities to capture excess wind and solar power using abandoned mine pits on the Iron Range. The concept involves pumping water to a higher elevation when energy demand and cost is low, then releasing the water through turbines when the energy demand is high. This is a collaborative effort between the University of Minnesota’s NRRI, St. Anthony Falls Laboratory and Humphrey School of Business with industry partners Minnesota Power and Great River Energy. In a similar manner, “Compressed Air” energy storage is also being examined to use underground mines and mine shafts with a range of storage capacity from 8.75 to 100 megawatts.


NRRI collected temperature data from 106 water wells and mineral exploration drill holes. Fifty-seven temperature measurements were compiled into 31 new heat flow sites to show that Minnesota has a much greater potential for enhanced geothermal energy production than was previously thought. NRRI has defined broad geothermal targets that show west and central regions of the state have the most suitable conditions, although new data is showing increased potential in northern Minnesota also. The next goal is to define viable geothermal targets for the state.

Cold Water Cooling

Use of deep sea water for air conditioning and other chilling applications is being done off the Kona Coast of Hawaii using sea water at depths of 5,000 to 6,000 feet. Lake Superior has water at similar temperatures at much shallower depths. NRRI is investigating the possibilities and implications of employing these energy saving technologies for Minnesota.
Consortium for Advanced Wood-to-Energy Solutions

NRRI is a key player in this collaboration of public and private sector institutions to advance sustainable, scalable, distributed wood-to-energy solutions. The group is committed to stimulating forest restoration and rural economic development through applied research. NRRI is involved in the Consortium’s focus on torrefaction by 1) demonstrating its use in electric power generation, 2) Optimizing the densification and 3) extending the current technology to use low value wood (with Georgia Southern University’s Advanced Materials Development Center).