Federal University of Itajub UNIFEI

Mechanical Engineering Institute IEM

Excellence Group in Thermal Power and Distributed G eneration NEST

MS.c Mateus Henrique Rocha

LIFE CYCLE ANALYSIS OF DIFFERENT ALTERNATIVES FOR THE TREATMENT AND

DISPOSAL OF ETHANOL VINASSE

1st Brazil-U.S. Biofuels Short Course

Providing Interdisciplinary Education in Biofuels Technology

So PauloJuly-August 2009

Ethanol production through sugar juice or finalmolasses fermentation has a serious problem related tothe quantities and high organic content of its mainresidue called vinasse or stillage.

For each liter of ethanol, 10-13 liters of vinasse areproduced using conventional technologies.

Ethanol vinasse is a dark, brown colour liquid, of acidnature, that remains after alcoholic distillation at 107C,with a smell that goes from astringent to nauseating.

Vinasse is classified as a class II residue, not inert butnot dangerous.

The chemical composition of sugarcane ethanolvinasse is variable and depends of the wine rawmaterials.

The wine characteristics depends also of the mustpreparation, alcoholic fermentation system, type ofyeast, distillation and flegma separation.

Chemical and physical properties of vinasse

Return to the farm, as a partial or total substitution ofmineral nutrients (fertirrigation).

Anaerobic digestion, using methanogenic bacterias, forthe production of biogas, process (anaerobic digestion).

Vinasse concentration by evaporation, for return tofarm as fertilizer.

Vinasse concentration by evaporation for combustionaiming at energy recovery.

The possible forms of vinasse disposal

Fertigation

Concrete typical channel Vinasse application rate (300 m/ha)

Distributed system by truck.

Anaerobic digestion

Anaerobic digestion plant: Flow = 5.000 m/day Diameter = 26,0 m Height = 4,75 m

Jenbacher Generator

Vinasse concentrated at 40%

Vinasse concentration by evaporation for combustion

Vinasse concentration

plants (Vogelbusch)

Concentrated vinasse at 60%.

Life Cycle Analysis (LCA) is a technique ofenvironmental analysis that allows the minimization ofenvironmental problems.

LCA is a process of evaluation of the environmentalimpacts associated with a system of products orservices, that allows the identification and evaluation ofthe impacts throughout the life cycle of the product.

Environmental impacts are determined based on theinputs and outputs of materials and energy in eachphase of the product life cycle, and can be associatedwith different categories.

Life Cycle Analysis

Main stages of a life cycle analysis study

Goal and Scope Definition

Goal and Scope

Definition

Inte

rpre

tatio

n

Impact Assessment

Inventory Analysis

Definition of the function, functional unit and reference flow

Product system establishment

Definition of the allocation procedures

Selection of environmental impacts

Data categorization

Studies supositions and limitations

Quality data requirements

Selection of the peer review process

Report definition

To establish the limits of the study.

Goal and Scope

Definition

Inte

rpre

tatio

n

Impact Assessment

Inventory Analysis

Inventory AnalysisGoal and scope definition

Preparation for data collection

Data collection

Data validation

Unit process data

Functional unit data

Data agreggation

Refining

To quantify the inputs and outputs of a product system.

Allocation and recycling

Goal and Scope

Definition

Impact Assessment

Inventory Analysis

Impact Assessment

Indicators

NormalizationAggregationWeighting

Data quality analysis Inte

rpre

tatio

n

Characterization

Characterization

Normalization

Normalization: contribution to the total impacth

hh~

=

Climate change 0.05%

Acidification 0.02%

Weighting (Single score)

Giving importance for each environmental impact

Subjective

Not to be used without appropriate Peer review for public purposes

== i ii h~

wh~

wW

(Non dimensional units)

Goal and Scope

Definition

Impact Assessment

Inventory Analysis

Inte

rpre

tatio

n

Interpretation

Sensitivity Analysis Evaluation

Materials selection Supply chain management Establish infrastruture for

recycling

Case study The objective of this work is to determine the environmentalimpact of disposal vinasse options and to compare them.

Functional unit: 1.0 m of vinasse treated.

System boundary: for inputs on the process the criterion of cutwill be mass flow, or potential of environmental impact of theproduct.

Selection of the methods of environmental impact evaluation :Eco-Indicator 99.

Requirement of the data: the data will be collected throughprimary sources (direct sample) or secondary (bibliographicalresearch).

Used software: for elaboration of the LCA data of vinasse will beused SimaPro 7.0 software elaborated by Pre Consultants, adutch Company.

Environmental impacts characterization

Environmental impacts characterization

Single score

Single score

Some remarks about LCA tool in cases studies

The application of LCA for the evaluation of environmental impacts related tovinasse treatment and disposal does not allow for a complete analysis, due tothe uncertainties associated to the leaching and volatilization of the vinasseapplied to the soil as fertilizer.

The presence of ions in vinasse, mainly potassium, phosphorus (phosphate)and nitrogen compounds (nitrite and nitrate) could cause groundwatersalinization.

The great obstacle concerning the quantification of this impact is the lack ofreliable information about what actually happens with vinasse componentswhen applied to the soil.

There are different possibilities in face of real situations: ions can behave asinert compounds and remain in the ground, to be converted into metabolites bymicroorganisms, extracted through roots for sugarcane nutrition, leached,volatilized to atmosphere, etc. Even when such information is available there isa great need of specialized scores for the correct evaluation of the relatedimpacts.

Some remarks about LCA tool in cases studies

The LCA results evaluation is also difficult due to the high amount of impactscores proposed in evaluation models, and the existing doubts in relation towhich of them preference must be given. Therefore, at the beginning of thestudy, while goal and scope were being defined, the impact evaluation modelsmust be clearly set, including the categories selection that would be considered,as well as, the compounds that would be taken into account during impactquantification.

Organic fertilizers, such as vinasse, present several advantages in relation tomineral fertilizers, as they promote nutrient recycling in ecosystems, and causeless environmental impacts during production. Currently great efforts are beingapplied in the research of renewable energy inputs, such as biogas andconcentrated vinasse, which contribute to the GHG reduction and climatechange mitigation.

Some remarks about LCA tool in cases studies

Life cycle inventory and associated energy balance do not allowfor the highlight of the advantages of cogeneration with thecommercialization of surplus electricity, due to the fact thatresidues energy potential is quantified using its heating value asreference. Final impacts evaluation must be carried out in order tocompare alternatives including cogeneration as by-productallocation method.

The comparison between these two environmental benefits, thatexclude each other, is a real gap in the ethanol sustainabilityevaluation. The cause of this is the existing uncertainties in co-products allocation and in the evaluation of fertirrigationsecondary impacts. Such gap has not been possible to be fulfilledusing LCA methodology in its current developing stage.

Thank you for attention!Thank you for attention!