Posts Tagged :

cultivo energetico

On Board with Energy Crops

300 140 Miguel Ángel Martínez

Near the Columbia River just outside of eastern Oregon’s Boardman sits the state’s last operating coal plant, a 600-MW facility built in the late 1970s. Though the plant has plenty of years left in it, the state’s decision to phase out coal left Portland General Electric exploring its options.

In 2010, PGE was approved to continue to burn coal at Boardman until 2020, with some temporary emissions controls upgrades. After that, $500 million in additional pollution controls would be required to comply with federal and state sulfur, nitrogen and mercury rules, thus enabling the plant to continue operations until at least 2040.

Ultimately, PGE faced three possibilities—closing by 2020, making costly upgrades, or switching to another fuel source. If closed, it would make history as the youngest coal plant in the U.S. to shut down as a result of air quality regulations, but doing so and building a new plant elsewhere makes more economic sense than keeping it open for upgrades.

With the upgrade option ruled out, the fate of the plant rests on the feasibility of using torrefied energy crops as fuel, and PGE has spent the past several years conducting in-depth research and rigorous testing to determine what the possibilities are.

Exploring Options

Initially, PGE looked into repowering with natural gas, but rendered that option unfeasible. “We did a study on natural gas and found the area didn’t have a gas line, but that wasn’t the real issue,” says Jaisen Mody, PGE projects manager. “The issue was that the Boardman boiler was designed for coal combustion, and using gas in the existing boiler made it highly inefficient. The cost wasn’t conducive to running the plant long-term, as we would have to change out the boiler. We decided that converting an old Rankine cycle coal boiler wasn’t the way to go because of the capital expenditure.”

Basically, it boiled down to the notion of using gas meant building a new gas plant, adds Steve Corson, PGE spokesman.

When PGE began evaluating biomass back in 2010, wood pellets were tested but gummed up the plant’s pulverizers. Crop research began at that point, and arundo donax was chosen as a fuel of interest due to its great growth potential. It’s been found to produce upwards of 35 dry tons per acre per year, compared to switchgrass, which will yield 4 to 13 dry tons per acre per year.

PGE has been growing arundo test plots around the Boardman area for the past couple of years—about 92 acres—and has harvested it a few times, storing the crop for test burns, Mody says. He adds that while the initial emphasis was mostly on arundo, that’s changed a bit.

On one hand, a single energy crop is attractive because it’s dedicated to producing feedstock volumes needed, but reliance on a single fuel source is risky for a number of reasons, including harsh weather, natural disasters or pests. “So we’re also investigating other biomass sources, including sorghum and ag waste,” says Mody.

One thing that’s certain is that if energy crops and biomass are used at Boardman, they will be torrefied first. “Torrefaction is the right way to repower Boardman with biomass, because we’re anticipating no changes to plant equipment,” Mody says.

Corson adds that torrefaction would allow the plant to pulverize the fuel just as it is doing with coal, but green biomass would require a lot of changes. Additionally, researchers have found that torrefied biomass is more hydrophobic than Powder River Basin coal, which is currently used at Boardman.

Later this year, PGE is installing a torrefier at Boardman, and will then begin its test burns, according to Mody. “These test burns are critical for us,” he says. “We think running this test will prove to us that we can run torrefied biomass through the plant, and we’ll also collect emissions data. Then we’ll sit down and figure out what it’ll take to run the plant for air permitting and the economics of that.”

Mody notes that each feedstock tested—arundo or sorghum—could have a different effect on the boiler, slagging or fouling it, so close attention will be paid as to what source is torrefied and how.

According to a study done in 2012 by researchers at the University of Washington, Washington State and Oregon State University, operating at 300 MW and producing power under optimal economic conditions, about 1.25 million tons of torrefied arundo would be used by Boardman, based on the Btu content of torrefied arundo (10,400 Btu per pound). About 94 dry tons of arundo would produce 52.7 tons of torrefied chips, the researchers found, so a total of 67.6 thousand acres of arundo would be required to produce 1.25 million tons of torrefied chips and support torrefaction, assuming 33 dry tons per acre per year.

Of course, while multiple sources would be used, Mody admits obtaining necessary quantities remains PGE’s biggest challenge in the quest to repower with biomass.

Moving Foward

“It’s [repowering] always been one issue—the source of biomass,” says Mody. “How can we procure and move enough in an economic manner that would sustain a large plant? The production of biomass, whether we’re growing or buying it, remains our biggest challenge. That’s why we’re looking at diversity now—one species isn’t the answer. It’s about what we can grow at a reasonable price, and what’s available out there.”

If the torrefaction test burns are successful, more work has to be done to calculate the economics and emissions profiles of a full-scale torrefier. Once that data is complete, PGE will bring it to its integrated resource planning process, which is a comprehensive plan presented to the public utility commission that lays out its generating portfolio resource requirements.

At that time, the next step for Boardman will be decided, Corson adds. “At this point, what we’ll really be saying is, okay, we know we can do this, is it better than the other options?”

Energy Crops for Biofuels

1024 554 Miguel Ángel Martínez

A number of energy crops can potentially be grown on marginal land (i.e. land that is not suitable for food production) to provide feedstocks for bioenergy, non-food products and biofuels. Examples of energy crops are shown below.

Using ‘contaminated’ land and ‘poor’ soils for biofuel feedstock production

Cultivation of energy crops can be used for phytoremediation of contaminated or poor soils, while offering the potential of future feedstock production. For example, see Multi-tasking plants for phytoremediation and bioenergy [Source: CABI 2013]. Globally, there is vast potential to grow energy crops on ‘contaminated’ land and poor soils, which are unsuitable for food crops. Current research is focused on trials of energy crop strains that could offer reasonable production potential. Typically, low nutrient levels, and inconsistent soils in marginal land tend to result in low yields, especially in initial years.

In August 2013, the U.S. EPA announced an update of its RE-Powering Mapping and Screening Tool, which has now identified 66,000 locations where contaminated land, landfill and mine sites could be used for cultivation of energy feedstocks.


Miscanthus - an energy crop© Copyright CPL Press
Miscanthus (above) has been trialled extensively in Europe and the US as an energy crop for biofuel production. Trials indicate that that it provides relatively high yields (double that of corn), requires limited fertiliser, few other inputs and adds significant amounts of organic matter to the soil. Othe giant grasses such as Switchgrass are also the subject of trials.

A ten year trial of Miscanthus (2003-2013) by University of Illinois showed an average annual yeild of 10.5 tons per acre (double that of a corresponding area planted with Switchgrass). The trial confirmed that Miscanthus grows well with little or no fertiliser input. After five years, the roots and rhizomes contribute 12 tons of biomass per acre to the soil (dry mass). The extensive root system of Miscanthus makes it suitable for stabilizing slopes or soils.

In March 2012 it was announced Mendel Biotechnology (Mendel Bioenergy Seeds) will carry out a 4-year field trial of PowerCane™ Miscanthus with BP Biofuels, as a potential feedstock for the cellulosic ethanol demonstration plant in Jennings.

Panicum virgatum (Switchgrass)

Extensive research is being carried out into cultivation of Switchgrass as a biofuels feedstock in the US. The plant is a tall-growing, perennial grass that is native to North America.

Samuel Roberts Noble Foundation has developed novel strains of switchgrass that contain lower amounts of lignin and hence boost biofuel yields by over a third [Source: Proceedings of the National Academy of Sciences].

Following a $5m grant from the DOE in 2009, University of Tennessee and Genera Energy have developed a new feedstock logistics systems using chopped switchgrass, which aims to bridge the gap between growers and biofuel producers.

Arundo donax (Giant reedgrass)

Miscanthus - an energy cropArundo donax (Giant reedgrass or Spanish cane) is considered to be one of the most promising species for biomass production in Europe. It is being cultivated as a feedstock for the Beta Renewables commercial scale cellulosic ethanol plant in Crescentino.

Sweet Sorghum

Sweet Sorghum - an energy crop© Copyright SWEETFUEL

Sweet sorghum, as a source of either fermentable free sugars or lignocellulosics, has many potential advantages, including: high water, nitrogen and radiation use efficiency; broad agro-ecological adaptation; rich genetic diversity for useful traits; and the potential to produce fuel feedstock, food and feed in various combinations. Further research on Sweet Sorghum is being carried out bySWEETFUEL – Sweet sorghum: an alternative energy crop (FP7 – 227422)

Sweet Sorghum is also being developed as a biofuel feedstock in the US (e.g.Regional Strategy for Biobased Products in the Mississippi Delta). In April 2013, construction started on a 20 MMgy sweet sorghum-to-ethanol plant in Florida [Ref:Southeast Renewable Fuels LLC ]. Also in the US, NexSteppe has developed low-input, high-yield Sweet Sorghum and ‘High Biomass Sorghum’ strains for use as bioenergy feedstocks. Ceres has also developed varieties of Swet Sorghum that are being commercially planted in Brazil. In March 2013, Chromatin signed an agreement to supply POET with Sorghum for its bioethanol plant in South Dakota. In November 2013, Arcadia Biosciences and DuPont Pioneer are collaborating on a project to use biotech and breeding techniques to improve the productivity of Sorghum.

Short Rotation Coppice (Willow and Poplar)

Short rotation coppice - harvesting© Copyright Choren
Willow and poplar may be grown and harvested in 2-5 year cycles as an energy crop (Short Rotation Coppice). SRC has potential for use as a feedstock for second generation biodiesel, for example as being demonstrated at the Choren BtL plant.

Sugar Cane

sugar cane harvestingSugar cane harvesting. Although sugar cane is a first generation crop, it is generally considered to be sustainable as it offers a high energy balance and high GHG reduction. It has not been shown to have significant impact on food supply or prices in Brazil, where there are 9 million vehicles that use ethanol or ethanol blends from sugar cane.

Phalaris arundinacea (Reed canary grass)

Phalaris arundinacea (Reed canary grass), provides good yields on poor soils and contaminated land and is thus an interesting candidate for bioremediation of brownfield sites as well as a source of biomass for bioenergy (typically as briquettes) or pulp. Is also considered a suitable feedstock for cellulosic ethanol production [Source: VTI Finland].


Flowers of the Jatropha treeCamelina sativa is an oil plant that grows well on marginal land, is cold-tolerant and has an oil-yield of 35-38%. It is being investigated as a sustainable oil crop for biodiesel production. Picture credit: Wikipedia.

Sustainable Oils (a partnership between Targeted Growth, Inc. and Green Earth Fuels, LLC) currently has 30 Camelina breeding trials in the US and Canada. The company provided Camelina-based biodiesel for a Japan Airlines test flight in January 2009.

The Eureka BIOFUEL-CAMELINA Project, coordinated by ISCO, Poland,
is studying the cultivation of Camelina sativa and cameline oil production, biofuel production and evaluation. Biojet fuel derived from Camelina has been successfully used on demonstration flights.


Flowers of the Jatropha tree
Flowers of the Jatropha treeImages of Jatropha curcas © copyright JatroSolutions GmbH, which offers expertise in tropical plant production, including cultivation of Jatropha for biofuel production. The top picture shows pollination of Jatropha by bees. The picture immediately above shows male flower (right) and female flower (left).

Jatropha curcas is a tropical plant that grows well on marginal land, is drought tolerant and has seeds with high oil content (~40%)*. Although the plant contains toxins, and has to be handled and processed with care, Jatropha is considered a good candidate as a biofuels feedstock and is the subject of various trials. For example, Archer Daniels Midland (ADM), Bayer CropScience AG and Daimler AGannounced in early 2009 that they would collaborate on use of Jatropha. NesteOilis also researching the use of Jatropha for biodiesel production. Galp Energia,Portugal is leading a research project on Jatropha for biofuels production in Mozambique.

*In Singapore, Temasek Life Sciences Laboratory and JOil Pte Ltd. have developed Jatropha strains with 75% oleic acid content, compared to the typical 45% percent (May 2012).

Salicornia bigelovii (dwarf saltwort / dwarf glasswort)

A salt mash halophyte that is found on both the east and west coast of the US and Mexico. The plant is of interest as a biofuel feedstock as it grows in desert environments, can be irrigated with seawater, and the seed contains around 30% oil content. It is being grown extensivley across the globe, for example in India.

Cynara cardunculus (Cardoon)

Cynara cardunculus (Cardoon) has been investigated as an energy crop for co-firing with lignite at the PPC Kardia Power Plant, Greece, as part of the FP6 DEBCOproject. The oil, extracted from the seeds of the cardoon (artichoke oil) has also been investigated as a feedstock for biodiesel production.

Brassica carianata (Ethiopian mustard)

Brassica carianata oilseed has been developed as a biofuel feedstock ( Resonance™) by Agrisoma Biosciences (Canada). It is suited to semi-arid areas and produces seed with 44% oil content. In April 2012 Agrisoma announced that Resonance™ will be evaluated as a feedstock for Honeywell Green Jet Fuel™.

Castor bean

Castor oil is also being developed as a potential industrial-scale biofuel feedstock. “Castor bean is a non-edible, high oil-yielding crop (40%-50% seed oil content) with high tolerance for growth under harsh environmental conditions, such as low rainfall and heat” [Source: Evogene].

FP7 Projects on energy crops

ENERGYPOPLAR aims to develop energy poplar trees with both desirable cell-wall traits and high biomass yield under sustainable low-input conditions to be used as a source of cellulosic feedstock for bioethanol production.

SWEETFUEL Sweet sorghum: an alternative energy crop (FP7 – 227422)


Virtual Modelling of Energy Crops

The Eureka E-PLANTS project led by Intesys has produced a 3D model of the virtual plant growth, enabling biofuel feedstock growers to visualise the complex and dynamic interactions between different plant components and experiment quickly with the simultaneous influences of temperature, nutrient levels, moisture and other conditions on rooting and growth.


Carbo-BioCrop project in the UK

Carbo-BioCrop will provide information on the carbon mitigation potential of bioenergy crops. The project is funded as part of the Living With Environmental Change (LWEC) project in the UK. The aim of Carbo-BioCrop is to gain a better understanding of the processes that cause changes in soil organic carbon (SOC) and emmissions of GHGs (CO2, N2O and CH4) under Short Rotation Coppice (willow, poplar) and Miscanthus. In particular, such changes will be quantified when land is converted from arbale or grassland to energy crops.

Support for Energy crops in the United States

In October 2010, USDA published a final rule to implement the Biomass Crop Assistance Program (BCAP). Under the BCAP final rule, USDA will resume making payments to eligible producers. The program had operated as a pilot, pending publication of the final rule. Authorized in the Food, Conservation, and Energy Act of 2008, BCAP is designed to ensure that a sufficiently large base of new, non-food, non-feed biomass crops is established in anticipation of future demand for renewable energy consumption.

Domestic production of renewable energy, including biofuels, is seen as a national imperative the USDA aims to help develop a thriving biofuels industry in every part of the US. A recent USDA report indicated that the initiative will will create jobs, combat global warming, replace our dependence on oil imports and boost the economy [Source: USDA].



Improving the sustainablility of first generation feedstocks

Although expansion of first generation biofuels has decreased since 2008, biodiesel and bioethanol are still produced from crops in existing plants (manufacturing facilities). In the medium term, a number of initiatives have been instigated to make feedstocks more sustainable, until second generation biofuels are available on a commercial scale.

Sustainable winter oilseed rape – 24 page brochure (2007) joint publication of Unilever N.V., and UFOP( UNION ZUR FÖRDERUNG VON OEL- UND PROTEINPFLANZEN E. V.). Also available for download in German (2.3 Mb PDF).

Certified palm oil 

Uso de cookies

Este sitio web utiliza cookies para que usted tenga la mejor experiencia de usuario. Si continúa navegando está dando su consentimiento para la aceptación de las mencionadas cookies y la aceptación de nuestra política de cookies, pinche el enlace para mayor información.plugin cookies

Aviso de cookies