From Pig to Fuel - Anaerobic digester generates energy, reduces odors

 Teng Lim is operating a small-scale anaerobic digester at the MU swine farm in Columbia. The system generates energy and can mitigate hog odor. Courtesy Jon Lamb.

The University of Missouri has unveiled a prototype small-scale anaerobic digestion system that produces biogas from pig manure. The biogas can be used to heat a farm and create electricity. The device also reduces odor from swine operations.

“What we want to do is improve and fully utilize all the biogas for energy production,” said Teng Lim, Extension Ag Systems Management associate professor.

Funded by the MU College of Agriculture, Food and Natural Resources, the anaerobic digester consists of three tanks. Manure from the hog barn pit is pumped into one tank where the manure is stored and mixed. The anaerobic digestion takes place in the other two tanks, where bacteria break down the manure in these warm and oxygen-free tanks.

The biogas from the manure can be used for electricity and hot water production. With some further treatment it can also be stored as a compressed natural gas, for heating or even vehicle fuel.

PigsLim says a larger scale digester could supply a farm’s energy needs and also be sold to the grid to provide electricity to the community.

There are other benefits to anaerobic digestion in addition to energy generation. The digested manure retains the nutrients to be good fertilizer while becoming a more consistent product. Also, the digester can reduce odor emissions.

“When the manure is treated by the digester process the odor concentration is significantly reduced,” Lim said. “There is still going to be odor, but it’s going to be much lower and less fluctuation than the raw manure.”

A Lot of Pork

The swine industry is big in the United States – there are 73,150 pork farms in America with 120 million pigs marketed each year.

Before the 1960s, most pork in the U.S. was raised in outside lots or on pasture systems. With the development of slotted floors and liquid manure handling equipment, it became possible for producers to more easily care for larger numbers of animals. Enclosed buildings overcame most weather problems and predators, and minimized the potential pollution from outside lot runoff.

Typically, pig odor is a localized air quality problem, with low concentrations of odorous gases such as p-cresol. Odor problems are often a starting point for litigation. Many farmers can go out of business just fighting a lawsuit.

An Important Part of Future Farms?

There are challenges to anaerobic digestion, the biggest being cost and management. In a commercial setting the digester would be 100 times larger than the one at MU’s swine research facility.

Lim pointed out that industry leaders and scientists believe anaerobic digesters will be an important piece of future farms, both to mitigate odor and for generating renewable energy.  The cost is a major obstacle now. The team is working closely with industry experts from Martin Machinery, a Missouri company who specializes in biogas generators and control systems.

MU researchers are using the scaled down digester to find ways to make digesters more affordable and easier to manage. They are also using it as an education tool to show producers the potentials, what it takes to process the manure, and to train people how to properly run a system like this.

Source: Cafnr

Silicon carbide increases energy efficiency

Illustration of the fill port of a silicon single crystal bar which has been prepared by the zone melting process. (Photo: TRUMPF Hüttinger)
To increase the efficiency of the power supply in industrial processes, thereby saving energy and CO2, the aim of the new joint "MMPSiC": Researchers at the Light Technology Institute (LTI) at the Karlsruhe Institute of Technology (KIT) examine together with the industrial partners TRUMPF Hüttinger and IXYS Semiconductor the use of power semiconductor switches of silicon carbide. The Federal Research Ministry is supporting the project with around 800,000 euros.

Of the semiconductor manufacturing over the coating of displays to processes in the automotive industry: Many industrial processes consume large amounts of electrical energy. Among these are technologies that will play an important role in the energy transition, as the zone melting method (float zone method) for producing high purity crystalline materials: The substance is electrically fused in a narrow zone; the melting zone is gradually continued. Behind the melting zone crystallized substance purer than before. The zone melting method provides, among other high-purity silicon single crystals for the manufacture of solar cells.

Power supply of zone melting systems based on tube technology systems are used to now having an electrical efficiency of up to 65 percent. By switching to power semiconductor silicon carbide, the efficiency of the process power supply could be increased to over 80 percent. This would save large amounts of electrical energy and reduce greenhouse gas emissions. For example, for a single float-zone scale plant would result consisting of 20 x 150 kW-process power supplies, with an annual duration of 4800 hours, a savings of more than 200,000 kWh of electrical energy and 109 tonnes of CO2 (Umweltbundesamt, as of July 2013).

The feasibility of such a process power supplies, researchers at the Light Technology Institute (LTI) of KIT together with the partners TRUMPF Hüttinger GmbH + Co. KG (Freiburg) and IXYS Semiconductor GmbH (Lampertheim) in the joint project "Modular medium frequency process power supply with silicon carbide semiconductor power switches" (MMPSiC) , As the semiconductor material Silicon Carbide offers several advantages: Thanks to the larger electronic band gap allows much higher operating temperatures than conventional semiconductors. Power electronics with silicon carbide is characterized by higher energy efficiency and compactness.

"When the power of energy-intensive industrial applications such as the zone melting method, it is necessary to switch at high frequencies," says the project director, Dr. Rainer Kling from LTI of KIT. "Silicon carbide is not yet tested for these high frequencies; so that we are breaking new ground. "In addition to examining the long-term stability include the control and the layout of the circuit to the tasks of the KIT researchers in the joint project MMPSiC.

The Federal Ministry of Education and Research (BMBF) supports MMPSiC project on the basis of the program "Information and Communication Technology 2020" (ICT 2020) as part of the funding program "Power electronics to increase energy efficiency" (LES 2) with around 800,000 euros. Of which receives the LTI KIT around 439,000 euros. Overall, the project volume is 1.3 million euros. The joint project started in 2014 and is planned for three years.

Source: KIT

Switching to vehicles powered by electricity from renewables could save lives

Driving vehicles that use electricity from renewable energy instead of gasoline could reduce the resulting deaths due to air pollution by 70 percent. Credit: © Dmitry Vereshchagin / Fotolia

Driving vehicles that use electricity from renewable energy instead of gasoline could reduce the resulting deaths due to air pollution by 70 percent. This finding comes from a new life cycle analysis of conventional and alternative vehicles and their air pollution-related public health impacts, published Monday, Dec. 15, 2014, in the Proceedings of the National Academy of Sciences.

The study also shows that switching to vehicles powered by electricity made using natural gas yields large health benefits. Conversely, vehicles running on corn ethanol or vehicles powered by coal-based or "grid average" electricity are worse for health; switching from gasoline to those fuels would increase the number of resulting deaths due to air pollution by 80 percent or more.

"These findings demonstrate the importance of clean electricity, such as from natural gas or renewables, in substantially reducing the negative health impacts of transportation," said Chris Tessum, co-author on the study and a researcher in the Department of Civil, Environmental, and Geo- Engineering in the University of Minnesota's College of Science and Engineering.

The University of Minnesota team estimated how concentrations of two important pollutants -- particulate matter and ground-level ozone -- change as a result of using various options for powering vehicles. Air pollution is the largest environmental health hazard in the U.S., in total killing more than 100,000 people per year. Air pollution increases rates of heart attack, stroke, and respiratory disease.

The authors looked at liquid biofuels, diesel, compressed natural gas, and electricity from a range of conventional and renewable sources. Their analysis included not only the pollution from vehicles, but also emissions generated during production of the fuels or electricity that power them. With ethanol, for example, air pollution is released from tractors on farms, from soils after fertilizers are applied, and to supply the energy for fermenting and distilling corn into ethanol.

"Our work highlights the importance of looking at the full life cycle of energy production and use, not just at what comes out of tailpipes," said Bioproducts and Biosystems Engineering Assistant Professor Jason Hill, co-author of the study. "We greatly underestimate transportation's impacts on air quality if we ignore the upstream emissions from producing fuels or electricity."

The researchers also point out that whereas recent studies on life cycle environmental impacts of transportation have focused mainly on greenhouse gas emissions, it is also important to consider air pollution and health. Their study provides a unique look at where life cycle emissions occur, how they move in the environment, and where people breathe that pollution. Their results provide unprecedented detail on the air quality-related health impacts of transportation fuel production and use.

"Air pollution has enormous health impacts, including increasing death rates across the U.S.," said Civil, Environmental and Geo- Engineering Associate Professor Julian Marshall, co-author on this study. "This study provides valuable new information on how some transportation options would improve or worsen those health impacts."

Source: University of Minnesota

Storing hydrogen underground could boost transportation, energy security

Salt caverns such as the one depicted here could provide a low-cost solution for the geologic storage of hydrogen. The colors in the illustration represent depth, with blue as the deepest part of the cavern and red the most shallow.
Credit: Sandia National Laboratories

Large-scale storage of low-pressure, gaseous hydrogen in salt caverns and other underground sites for transportation fuel and grid-scale energy applications offers several advantages over above-ground storage, says a recent Sandia National Laboratories study sponsored by the Department of Energy's Fuel Cell Technologies Office.

Geologic storage of hydrogen gas could make it possible to produce and distribute large quantities of hydrogen fuel for the growing fuel cell electric vehicle market, the researchers concluded.

Geologic storage solutions can service a number of key hydrogen markets since "costs are more influenced by the geology available rather than the size of the hydrogen market demand," said Sandia's Anna Snider Lord, the study's principal investigator.

The work, Lord said, could provide a roadmap for further research and demonstration activities, such as an examination of environmental issues and geologic formations in major metropolitan areas that can hold gas. Researchers could then determine whether hydrogen gas mixes with residual gas or oil, reacts with minerals in the surrounding rock or poses any environmental concerns.

Storage seen as key to realizing hydrogen's market growth

Should the market demands for hydrogen fuel increase with the introduction of fuel cell electric vehicles, the U.S. will need to produce and store large amounts of cost-effective hydrogen from domestic energy sources, such as natural gas, solar and wind, said Daniel Dedrick, Sandia hydrogen program manager.

As Toyota, General Motors, Hyundai and others move ahead with plans to develop and sell or lease hydrogen fuel cell electric vehicles, practical storage of hydrogen fuel at large scale is nessesary to enable widespread hydrogen-powered transportation infrastructure. Such storage options, Dedrick said, are needed to realize the full potential of hydrogen for transportation.

Additionally, installation of electrolyzer systems on electrical grids for power-to-gas applications, which integrate renewable energy, grid services and energy storage will require large-capacity, cost-effective hydrogen storage.

Storage above ground requires tanks, which cost three to five times more than geologic storage, Lord said. In addition to cost savings, underground storage of hydrogen gas offers advantages in volume. "Above-ground tanks can't even begin to match the amount of hydrogen gas that can be stored underground," she said.
The massive quantities of hydrogen that is stored in geologic features can subsequently be distributed as a high-pressure gas or liquid to supply hydrogen fuel markets.

Model helps identify the most favorable storage locations
While geologic storage may prove to be a viable option, several issues need to be explored, said Lord, including permeability of various geologic formations.

A geologist in Sandia's geotechnology and engineering group, Lord for years has been involved in the geologic storage of the U.S. Strategic Petroleum Reserve, the world's largest emergency supply of crude oil.

For her study on geologic storage, Lord and her colleagues analyzed and reworked the geologic storage module of Argonne National Laboratory's Hydrogen Delivery Scenario Analysis Model. To help refine the model, Lord studied storing hydrogen in salt caverns to meet peak summer driving demand for four cities: Los Angeles, Houston, Pittsburgh and Detroit.

She determined that 10 percent above the average daily demand for 120 days should be stored. She then modeled how much hydrogen each city would need if hydrogen met 10, 25 and 100 percent of its driving fuel needs.

Los Angeles has three times the population of Detroit and more than six and a half times the population of Pittsburgh, but the nearest salt formations are in Arizona, so Lord included the cost of getting the stored hydrogen from Arizona to Los Angeles.

Even so, Los Angeles' modeled costs are significantly less than those for Detroit and Pittsburgh. Salt formations in Arizona are thicker than those for Detroit and Pittsburgh, with larger and fewer caverns. Houston has the best conditions of the four cities because the Gulf Coast offers large, deep salt formations.

To examine the cost of geologic hydrogen storage, Lord started by selecting geologic formations that currently store natural gas. Working with Sandia economist Peter Kobos, Lord analyzed costs to store hydrogen gas in depleted oil and gas reservoirs, aquifers, salt caverns and hard rock caverns.

Their paper, "Geologic storage of hydrogen: Scaling up to meet city transportation demands," was published in the International Journal of Hydrogen Energy.

A geologic solution for peak period storage
Other fuels are already stored geologically. Oil from the Strategic Petroleum Reserve, for example, is held in large man-made caverns along the Gulf Coast. Natural gas is stored in more than 400 geologic sites to meet winter heating demands.

Lord envisions that excess hydrogen produced throughout the year could be brought to geologic storage sites and then piped to cities during the summer, when the demand for driving fuels peaks.

Depleted oil and gas reservoirs and aquifers initially seem the most economically attractive options, she said. "Just looking at numbers, because they can hold such a larger volume relative to any cavern you create, they look cheaper," she said.

But hydrogen gas is a challenging substance to store. "Because it's a smaller molecule than methane, for example, it has the potential to leak easier and move faster through the rock," Lord said.

Depleted oil and gas reservoirs and aquifers could leak hydrogen, and cycling -- filling a storage site, pulling hydrogen out for use and refilling the site -- can't be done more than once or twice a year to preserve the integrity of the rock formation, Lord said.
With a salt cavern or hard rock cavern, "there are no permeability issues, there's really no way anything can leak," she said. "You can bring more product in and out, and that will, in the long run, decrease your costs."

Hard rock caverns are relatively unproven; only one site holds natural gas. But salt caverns, which are created 1,000 to 6,000 feet below ground by drilling wells in salt formations, pumping in undersaturated water to dissolve the salt, then pumping out the resulting brine, are used more extensively and already store hydrogen on a limited scale, Lord said.

Future challenges

Lord said her work could lead to demonstration projects to further cement the viability of underground hydrogen storage. Salt caverns are the logical choice for a pilot project due to their proven ability to hold hydrogen, she said. Environmental concerns such as contamination could also be further analyzed.

However, salt formations are limited. None exist in the Pacific Northwest, much of the East Coast and much of the South, except for the Gulf Coast area. Other options are needed for development of a nationwide hydrogen storage system.

Lord's work adds to Sandia's capabilities and decades of experience in hydrogen and fuel cells systems. Sandia leads a number of other hydrogen research efforts, including the Hydrogen Fueling Infrastructure Research and Station Technology (H2FIRST) project co-led by the National Renewable Energy Laboratory (NREL), a maritime fuel cell demonstration, a development project focused on hydrogen-powered forklifts and a recent study of how many California gas stations can safely store and dispense hydrogen.

Source: Sandia National Laboratories