Interesting data from a Feasibility Study on Ethanol Production from Sweet Sorghum

by   Irene Tsakiridou

November 07, 2011

The “Feasibility Study Integrated Anhydrous Alcohol Production Plant using Sweet Sorghum as Feedstock”, of the International Society for Southeast Asian Agricultural Sciences, 2007, presents a model of producing ethanol from sweet sorghum in Philippines. The study team presents some very interesting data as shown below.

Sweet sorghum holds great advantages given its high productivity and low production cost. Thus there is a great potential of revenues for the farmers in cultivating sweet sorghum in comparison to sugarcane and to an improved variety of corn. An average feedstock price for the stalks of sweet sorghum is 0.214 €/litre for a yield of 5,625 Litre/ha/year. The table below gives the respective data for the grain of sweet sorghum as presented in the study.

Sweet sorghum

Feedstock price/litre

Litre/ha/year

stalk

0.214 €/litre

5,625

grain

0.325 €/litre

2,513


Location of the bioethanol distillery.

The authors of this study also declare that the strategic location of the bioethanol distillery is near to the farm production areas and the depots of the oil companies (60-80% of the total production cost of bioethanol derives from the feedstock accounts). Other factors to be considered in the selection of the location are the logistics (i.e road infrastructure, port and handling facility, appropriate transport, storage) the site size, access to a high voltage three-phase tapping point , even if it has its own power generator, the availability of water as distilleries consumes 25-175 litres of water per 1litre of alcohol. Moreover distilleries located near to the depots advance in other areas located near to the ports because as it is explained “Bioethanol is hygroscopic and cannot be handled by the current petroleum infrastructure without modification in the infrastructure. The current petroleum transport infrastructure, such as ships and pipelines rely on water to move petroleum products. Mixing ethanol into gasoline modifies its characteristics, making it difficult to separate out water. And too much water in the fuel affects the engine performance and service life”. The study gives a list summarizing the factors to be considered and it is presented in the next table.

Feedstock

• historic prices of feedstock

• competition for feedstock

• feedstock availability or easy acceptance and handling of trucks

• proximity of feedstock to plant

• seasonality of the feedstock

Water

• well water (actual availability and water quality must be thoroughly investigated)

• river water (for non contact cooling)

• water quality (mineral content)

• adequate wastewater disposal options

Energy

• proximity to three-phase tapping point

• reliability of local utility

• low utility rates

• availability of good long term contracts

• access to technologically established alternative energy sources

• power cogeneration potential

Transportation

• access to good roads

• access to rail for larger distilleries

Market Access

• geographical market potential

• proximity to gasoline blending terminals

• adequate trucking

• adequate port and shipping services

• potential for carbon dioxide market

Site Size

• ample room for future capacity expansion

• adequate space for truck traffic to move with ease

• adequate space for feedstock storage

• space for water treatment facility

• space for composting of distillery slops and other wastes

• space for run-off lagoon, if required, on the plant property

• proper ethanol and denaturant storage facilities with adequate storage volumes

• ample space for efficient ethanol and co product loading facilities


Standard of bioethanol.

According to the Bureau of Product Standards of the Department of Trade and Industry in Makati City, the complete standard is presented in the study and is presented in the following table.

Physical properties of bioethanol*

Specific gravity

0.79 gm/cm3

Vapor pressure (380)

50 mm Hg

Boiling temperature

78.50C

Dielectric constant

24.3

Water solubility

Chemical properties of bioethanol*

Formula

C2H5OH

Molecular weight

46.1

arbon (wt)

52.1%

Hydrogen (wt)

13.1%

Oxygen (wt)

34.7%

C/H ratio

4.0

Stechiometric ratio (Air/ETOH)

9.0

Thermal properties of bioethanol*

Lower heating value

6,400 kcal/kg

Ignition temperature

350C

Specific heat (kcal/kg-0C)

60

Melting point

-1150C

 *Source: Latin America Thematic Network on Bioenergy, 2006

Transportation of feedstock.

The sweet sorghum stalks may be transported to the distillery via truck but in case the plantations are 50km away from the final destination it is recommended to extract the juice from the stalks and convert it into syrup/concentrated juice. The process of making syrup is extraction of juice, collection, filtration and boiling. In Philippines most producers use 5HP engines driving three metal rollers, each engine is able to squeeze around 300 kg stalks per hour. The remained stalks after they are dried in opened fields may be used as an energy source for boiling the juice. The grains of sweet sorghum can be processed as corn grain and transported via trucks to the distillery. The following image taken from the same study indicated the production chain of ethanol from sweet sorghum stalks and grains.

Yield of sweet sorghum.

Regarding the yield of sweet sorghum the study team reports the following. The production of bioethanol from sweet sorghum and more specifically from the variety ICR 93034 is estimated at about 350–370 l/tn of sweet sorghum juice. The juice extracted is about 222 kg per tn of stalks, while the sweet sorghum concentrated juice is 2016 tn/ha. The cultivation cost of sweet sorghum is 9.2€/tn. When the juice is delivered to the unit, its price varies at 76.99–87.42 €/tn. The following table. presents the related data in average numbers.

Country

Philippines

year

2007

Sw variety

ICR 93034

sw  juice/stalks litre/tn

222

sw concentrated juice/stalks liter/tn

41

Stalk yield/ha,  tn /ha

49

sw juice/ha , litre/ha

10894

sw concentrated juice/ha , litre/ha

2016

sw concentrated juice/stalks,  litre/tn

41,1

Sugar content of  juice Brix

18

Sugar content of concetrated juice Brix

87-92

cooking time, min

155

Litre of ethanol/ litre of sw concentrated juice

360

Cost of sw juice production €/liter

0,37

Cultivation Cost of Sw stalks €/tn

9,2

Sale of sw juice €/tn

23,6

Sale of sw concetrated juice €/tn

84,4

Transportation cost of sw stalks €/tn

41,8