Sweet sorghum produces more ethanol per acre at lower cost

Originally published at University of Nebraska–Lincoln Department of Agronomy & Agriculture
by Dr. Ismail Dweikat

Sweet sorghum is a drought-tolerant feedstock with the potential to produce more ethanol/acre than corn

To learn more about sweet sorghum or related research by UNL faculty/staff, please contact Dr. Ismail Dweikat by email or by phone at 402-472-5328.
To learn more about sweet sorghum or related research by UNL faculty/staff, please contact Dr. Ismail Dweikat by email at: idweikat2@unl.edu or by phone at: 402-472-5328. Image credit: University of Nebraska–Lincoln Department of Agronomy & Agriculture

Sweet sorghum stalks contain up to 75% juice, varying between 12 and 23% in sugar. There’s enough juice in an acre of sweet sorghum to make 400 to 800 gallons of ethanol.

Sorghum juice-derived ethanol is cheaper to produce than corn ethanol because it doesn’t require the cooking and enzymes that corn requires for conversion of starch to sugar to fuel grade alcohol.

Current estimates suggest that intensive plant breeding and cultivation research could, over time, increase the sugar content of sorghum juice to a level needed to produce 1000 gallons of ethanol per acre. We plan to evaluate the potential of sweet sorghum as an ethanol-producing crop for Nebraska.

Sweet sorghum is a perennial crop in areas that don’t have a winter freeze. Plant breeding efforts continue to improve the cold tolerance of sorghum for growth in the Midwest.

In the Corn Belt, sweet sorghum grows 10 to 15 feet tall during a growing season. The taller the plant and the thicker the stalk, the more juice the plant will produce. To maximize juice and ethanol production in the Corn Belt, growers need to plant the crop early to mid-April. The grower could then make the first cutting for juice in early July, when the crop starts to flower. A second cutting could be made in October, shortly before frost, yielding enough juice for an additional 100 to 200 gallons of ethanol.

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Image credit: University of Nebraska–Lincoln Department of Agronomy & Agriculture

Or, if feed were short, the grower could hay or graze the second cutting. Sweet sorghum’s energy-savings and value emerge in several ways:

  • The crop only needs 12-15 inches of rain during the growing season to make a crop. Therefore, it is suitable for dryland production or limited irrigation. If the crop receives more moisture, it will respond positively.
  • It requires only 40-60 lbs of nitrogen per acre. The crop is long-rooted and can extract residual nitrogen left by previous crops, or from nitrogen-fixing soybeans preceding in rotation.
  • Sweet sorghum juice doesn’t require the long fermentation and cooking time needed to process corn ethanol.
  • Some of the crop residue left after juice extraction (called bagasse) can be dried and burned to fuel ethanol distillation. These residues can also be used for animal feed, paper, or fuel pellets.
  • The crop needn’t be grown on a farmer’s best land, allowing the farmer to make use of poorer ground.
  • The simplicity of ethanol production from sweet sorghum could lend itself to on-farm or small-cooperative efforts at fuel-making.
  • Ethanol plants in the State could choose, with some additional equipment, to make seasonal runs of sweet sorghum juice.

Ethanol is currently processed from sweet sorghum in Texas, Oklahoma, and Iowa, as well as India and other parts of the world. We seek to enhance sweet sorghum performance on marginal lands, and to identify a strategy for improving its ethanol processing potential, two key components for developing this system for production in Midwest region.

University of Nebraska’s efforts to improve sweet sorghum’s yield potential as an ethanol feedstock

The University of Nebraska Sorghum Breeding Program possesses an extensive collection of sweet sorghum germplasm ranging in maturity period, photoperiod sensitivity, height, total biomass production and brix readings from 12 to 23%.

Our objectives for improving sweet sorghum include;

  1. Perform life-cycle analysis of sweet sorghum and triticale-ethanol systems for net energy yield, efficiency, and potential to mitigate greenhouse gases as compared to other biofuels, such as corn grain-ethanol and petroleum-derived gasoline.
  2. Conduct chemical and fermentation analysis of a) sweet sorghum sap for maximum conversion to ethanol and b) sorghum stover for cellulosic ethanol production.
  3. Sweet sorghum stover also serves as an excellent feedstock for ethanol production. Stover contains lignin, hemi-cellulose, and cellulose. The hemi-cellulose and cellulose are enclosed by lignin (which contains no sugars), making them difficult to convert into ethanol, thereby increasing the energy requirement for processing. The brown midrib (bmr) mutants of sorghum have significantly lower levels of lignin content (51 percent less in their stems and 25 percent less in their leaves). Research showed 50 percent higher yield of the fermentable sugars from the stover of certain sorghum bmr lines after enzymatic hydrolysis. Therefore, the use of bmr cultivars would reduce the cost of biomass-based ethanol production and these lines will be incorporated into our experimental approach. We have moved two bmr genes to sweet sorghum line and hybrids.
  4. We have identified genetic variation for cold tolerance in sorghum. The improved lines have the capacity of germination at 50 degrees F soil temperature. Because of these traits, we have been able to plant our sorghum trails in the first two weeks of April for the past three years. Due to this, growers will be able to plant their sorghum crops at the same time they plant their corn. Usually, we have to wait till the second week of May to plant the sorghum crop. We also have introduces into sorghum genes that confer stress resistance (cold, drought and salt stress) from other crops via genetic transformation.
  5. We are also selecting for non-flowering high sugar types in order to extend the growing season and total biomass. Beside the non-flowering type, we are developing sterile F1 hybrids.
  6. To develop management practices that achieve high water and nitrogen use efficiency while maintaining high sugar yields in sweet sorghum. Because sorghum harvested for biomass can be harvested before maturity, it is possible to grow it in a double-crop sequence with a winter annual. Hairy vetch (Vicia villosa Roth) is a moderately winter-hardy legume that can be seeded in fall and reach maturity by early summer. Hairy vetch is capable of producing as much as 3-5 tons/acre and leave up to 100 lb on nitrogen in the soil which sufficient to grow a full crop of sweet sorghum. Vetch will be planted in October after the sweet sorghum harvest, and will be harvested in early May followed by a sweet sorghum planting on May 15.
stalks-web.jpg
Sorghum stalks range in diameter from 4.5 to 1.5 cm. Image credit: University of Nebraska–Lincoln Department of Agronomy & Agriculture

This article has been republished at Biofuel Central with the kind permission of Dr. Ismail Dweikat of the University of Nebraska–Lincoln Department of Agronomy & Agriculture

Shell and Cosan invest $1 billion to boost Brazilian biofuels

Royal Dutch Shell and Cosan Ltd. invest $1 billion to boost Brazilian biofuels | 30/12/14
by John Brian Shannon John Brian Shannon

Everyone knows that Royal Dutch Shell is a giant in the global petroleum industry, but did you know that Raízen (Shell and Cosan’s joint biofuel venture) is Brazil’s 3rd-largest energy company?

Raízen, the joint venture between Royal Dutch Shell and Cosan Ltd, is the third-largest energy company in Brazil in terms of revenue. Image courtesy of Raízen.
Raízen, the joint biofuel venture between Royal Dutch Shell and Cosan Ltd. is the 3rd-largest energy company in Brazil. Image courtesy of Raízen.

Now Shell the petroleum giant and Cosan the sugar giant have teamed up to invest $1 billion dollars over the next 10 years in 2nd generation biofuels sourced from sugarcane. The sweet part of this deal (apart from the sugarcane) is that both companies have committed to bring 1st generation biofuel production practices to an end, replacing those practices with 2nd generation technology, making Brazilian biofuel orders-of-magnitude cleaner.

Growing sugarcane for biofuel in Brazil usually means harvesting the cane of the sugarcane plant, leaving the rest of the plant behind. All of the ‘bagasse’ or ‘stover’ as it’s sometimes called, goes up in smoke as the fields are burned by the farmers twice per year. (Due to Brazil’s climate and nutrient-dense soil, sugarcane growth is explosive and Brazilian farmers can harvest 2 crops of sugarcane per year)

So much smoke and CO2 is generated from this 1st generation practice that NASA says it is able to detect changes in the Earth’s airmass for many weeks after millions of acres of sugarcane fields are burned in Brazil.

Happily, that’s going away now as Raízen will harvest the bagasse immediately after the main sugarcane harvest and process it with enzymes in cellulosic bioreactors, converting it into very pure ethanol.

All the benefits of ethanol biofuel — but without the (1st generation) drawbacks

Nothing will change with regards to the same fast, reliable, and simple process presently employed to produce biofuel from the sugarcane itself.

But harvesting the bagasse, changes everything as millions of acres of fields no longer need to be burned twice per year in order to remove the millions of tonnes of leftover plant material.

Due to advances in cellulosic biofuel technology, the leaves, roots and other parts of the sugarcane plant can be used in new cellulosic biofuel reactors (basically, a 500,000 gallon soup pot) to produce very high quality ethanol (or biodiesel, depending on the enzymes chosen and the process employed) at a moderate cost.

Raízen will increase their annual biofuel output by 50% to 1 billion litres — which is roughly equivalent to 106 million US gallons.

No doubt that most of this newfound ethanol will be used to power cars within Brazil as all gasoline in the country must have a minimum 25% ethanol component — known as the E25 blend. If you choose the ‘other pump’ at the gas station, you can fuel your car with 100% ethanol, assuming your car is E100 compatible.

There are no longer any light vehicles in Brazil running on pure gasoline.

Since 1976 the government made it mandatory to blend anhydrous ethanol with gasoline, fluctuating between 10% to 22%, and requiring just a minor adjustment on regular gasoline engines.

In 1993 the mandatory blend was fixed by law at 22% anhydrous ethanol (E22) by volume in the entire country, but with leeway to the Executive to set different percentages of ethanol within pre-established boundaries.

In 2003 these limits were set at a minimum of 20% and a maximum of 25%. Since July 1, 2007 the mandatory blend is 25% of anhydrous ethanol and 75% gasoline or E25 blend.

The Brazilian car manufacturing industry developed flexible-fuel vehicles that can run on any proportion of gasoline (E20-E25 blend) and hydrous ethanol (E100).

Introduced in the market in 2003, flex vehicles became a commercial success, reaching a record 92.3% share of all new cars and light vehicle sales for 2009.

By December 2009 they represented 39% of Brazil’s registered Otto cycle light motor vehicle fleet, and the cumulative production of flex-fuel cars and light commercial vehicles reached the milestone of 10 million vehicles in March 2010, and 15.3 million units by March 2012.

By mid-2010 there were 70 flex models available in the market manufactured from 11 major carmakers.

The success of “flex” vehicles, together with the mandatory E25 blend throughout the country, allowed ethanol fuel consumption in the country to achieve a 50% market share of the gasoline-powered fleet in February 2008.

In terms of energy equivalent, sugarcane ethanol represented 17.6% of the country’s total energy consumption by the transport sector in 2008. — José Goldemberg, the father of the Brazilian biofuel industry, as quoted by CleanTechnica.com

If all ethanol producers in Brazil follow Raízen’s lead, the country could soon be exporting millions of litres of very pure (clean burning) and very clean (sustainable agriculture practices) ethanol biofuel.

As far as the cost is concerned, producing second generation cellulosic oil is more costly than that of ethanol, produced from other sources. Raizen’s Agro-Industrial Director, Joao Alberto Abreu, expects costs to decrease over time as enzymes needed for production become more easily available.

Brazil is the biggest ethanol producer in the world and one of the biggest exporters of biofuel.

Many ethanol producers have been struggling over the past few years but there are encouraging signs as domestic demand for ethanol is on the rise, while the opportunity to export cellulosic ethanol might grow in the near future.

It looks like 2nd generation biofuel production practices have won in Brazil. Competitors will be forced to emulate Raízen’s lead, rather than continue to send billions of dollars worth of product up in smoke at each harvest.

All in all, a very sweet deal. Congrats to Shell and Cosan on their Raízen joint venture!