A model for producing ethanol from sweet sorghum in the Philippines

by   Dr. Kostas KONSTANTINOU

July 06, 2012

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 the 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 declare that the strategic location of the bioethanol distillery is near  the farm production areas and the depots of the oil companies (60-80% of the total production cost of bioethanol derives from the feedstock transportation costs). 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 and the availability of water as distilleries consume 25-175 litres of water per 1litre of alcohol. Moreover distilleries located near to the depots advance in other areas located near the ports because 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.

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.

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

source: “Integrated Anhydrous Alcohol Production Plant using Sweet Sorghum as Feedstock”