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The environmental impacts of the transformation of cassava roots into starch were assessed for three contrasting technologies at small (ST1, ST2) and very large scale (VLT), meaning 1-2 and 100-200t starch per day, respectively. The goal of the study was to assess energy and water use for each unit operation, so as to identify high usage hotspots. The Life Cycle Assessment (LCA) framework was applied in order to test its relevance as a tool to analyze unit operations’ environmental performance, for process eco-engineering purposes.
Methods
Conclusions
An assessment of environmental impacts
of cassava starch extraction technologies
T. Tran
a,*
, G. Da
b
, K. Piyachomkwan
f
, M. Moreno
c
,
G. Velez
d
, A. Giraldo-Toro
e
, K. Sriroth
f
, D. Dufour
a,e
aCentre de coopération internationale en recherche agronomique pour le développement (CIRAD), Persyst Department,
UMR Qualisud, TA-B95/15, 73 rue JF Breton, 34398 Montpellier, France
bCERTES, Université Paris-Est Créteil, 61 avenue du Général de Gaulle, 94000 Créteil, France
cUniversidad del Valle (UniValle), Cali, Colombia
dDeriyuca LTDA. Carrera 89 # 10-80 apartamento 323 - Multicentro - Unidad 20-21, Cali, Colombia
eInternational Center for Tropical Agriculture (CIAT), Km 17 Recta Cali-Palmira, Cali, Colombia
fCassava and Starch Technology Research Unit (CSTRU / BIOTEC), Kasetsart University, Jatujak, Bangkok 10900, Thailand
* Corresponding author: Tel +33-467615847; E-mail thierry.tran@cirad.fr
The system boundaries were defined as the unit operations used to transform fresh cassava roots delivered at factory gate into loose, dry cassava starch (figure 1). The functional unit (FU) was defined as one ton of loose, dried cassava starch (i.e. starch at 12% moisture content on a wet weight basis, wwb), obtained at the end of the manufacturing process.
Primary data for ST1 and ST2 factories were obtained from the authors’ own measurements in collaboration with one cassava starch factory based in Vietnam (suburban Hanoi region) and one based in Colombia (Cauca department). Data for the VLT factory and data related to water and
chemicals consumption (e.g. alum, SO2) were
based on measurements published by Piyachomkwan et al. (2005), Sriroth (1996) and Sriroth et al. (2000) in Thailand. The factories surveyed were representative of the standard technology used in the three regions of the study.
Energy and water consumption varied widely between technologies (figures 2 & 3). The large scale technology required 702kWh/t starch, mainly (75%) from fuel oil used for the drying operation, but was the most
efficient in terms of water use (10m3/t starch) due to the practice of water
recycling between unit operations. The two small scale technologies were similar in terms of electricity use (59kWh/t starch), and were able to rely on solar energy for drying, due to the small volumes of production. In contrast,
water consumption varied from 20 to 60m3/t starch between the two small
scale technologies due to differences in the design of the rasping and starch recovery (extraction) operations.
Among the three technologies assessed, markedly different levels of energy and water consumption were identified for some unit operations, such as extraction or root washing, which indicates the potential for technology transfers and improvements of the overall environmental performance of the cassava starch industry.
This work demonstrates the feasibility and usefulness of applying LCA concepts for integrating environmental performance indicators in the design and evaluation of transformation processes for agro-industrial products. The environmental dimension should come in addition to other aspects including process yields, microbial safety and product quality.
Introduction
Results
WASHING RASPING DEWATERING EXTRACTION SEPARATION Starch (12% moisture)Fresh Cassava Roots
DRYING F a c to ry
Results (continued)
The LCA characterizations (figure 4), using the ReCiPe method, indicated that the main impact contributions were at the drying operation for the large scale technology, and at the extraction operation for the small scaletechnologies, mainly because of energy use, as well as water use in the case of the most water-intensive technology.
Figure 1: Unit operations of the cassava starch extraction process. The dotted line represents the selected system boundaries.
Acknowledgments
Stakeholders of the cassava starch industry in Vietnam and Colombia, and staff and students at HUST and CIAT, who made possible the data collection. The support of Le Thanh Mai from HUST regarding the electricity mix in Vietnam is gratefully acknowledged. The authors thank CIRAD and CIAT for financial support.
45.6 22.1 13.6 50.3 33.2 34.7 33.0 28.4 2.2 1.6 0.3 2.3 8.1 4.3 45.6 50.3 33.0 28.4 540.3 0% 20% 40% 60% 80% 100% VLT Electricity + fuel oil; 702.2kWh/t VLT Electricity only; 161.9kWh/t ST1; 59.2kWh/t ST2; 58.6kWh/t
Drying - Fuel oil Drying - Elec Separation Extraction Rasping Root washing Water pump
Figure 2: Energy consumption by unit operations of VLT, ST1 and ST2 technologies (large, small 1 and small 2 respectively). The figures within the bars and on the horizontal axis indicate actual energy use per operation and total energy use respectively, in kWh/t starch.
2.0 9.1 11.8 2.8 6.9 6.2 18.8 31.9 7.4 3.6 18.3 0% 20% 40% 60% 80% 100% VLT; 9.8m3/t ST1; 20.8m3/t ST2; 62.1m3/t Separation - Recycled Separation Extraction - Recycled Extraction Rasping - Recycled Rasping
Root washing - Recycled Root washing
Figure 3: Freshwater consumption by unit operations of VLT, ST1 and ST2 technologies. The figures within the bars and on the horizontal axis indicate actual water use per operation and total water use respectively, in m3/t
starch. 0% 20% 40% 60% 80% 100% Clim ate ch ange Ozo ne d eple tion Human toxi city Photo chem ical o xidant form atio n Parti cula te m atte r for matio n Ionisi ng ra diatio n Terre stria l aci dificat ion Fres hwat er e utro phic atio n Mar ine eu troph icatio n Terre stria l eco toxi city Fres hwat er e coto xicity Mar ine ec otoxic ity Agric ultu ral l and occu patio n Urban land occ upat ion Natural land tran sform atio n Wat er dep letio n Metal dep letio n Foss il depl etio n Drying Centrifugation Separation Extraction Rasping Washing VLT 0% 20% 40% 60% 80% 100% Clim ate ch ange Ozo ne d eple tion Human toxi city Photo chem ical o xidant form atio n Parti cula te m atte r for matio n Ionisi ng ra diatio n Terre stria l aci dificat ion Fres hwat er e utro phic atio n Mar ine eu troph icatio n Terre stria l eco toxi city Fres hwat er e coto xicity Mar ine ec otoxic ity Agric ultu ral l and occu patio n Urban land occ upat ion Natural land tran sform atio n Wat er dep letio n Metal dep letio n Foss il depl etio n Drying Sedimentation Separation Extraction Rasping Washing ST1 0% 20% 40% 60% 80% 100% Climat e chan ge Ozone dep letio n Hum an to xicity Photo chem ical oxi dant form atio n Par ticul ate m atte r form ation Ioni sing ra diat ion Terr estri al a cidific ation Fres hwat er eut rophic atio n Marin e eutro phic atio n Terr estri al eco toxi city Fres hwat er eco toxi city Marin e ecot oxic ity Agr icul tura l lan d oc cupa tion Urban land occup atio n Nat ural land tran sfor mat ion Wat er d eple tion Metal dep letio n Foss il depl etion Drying Sedimentation Separation Extraction Rasping Washing ST2
Figure 4: Environmental impacts characterization of the transformation of cassava roots into starch for the very large scale (VLT) and two small scale (ST1, ST2) technologies.
