This study assessed the environmental and economic potential of producing bioethanol from banana and plantain waste in Costa Rica. Interviews found that 40% of cooking bananas are left to rot, generating over 2800 tons of annual waste that could be converted to 193,000 liters of bioethanol. This bioethanol could replace 24% of the cooperative's gasoline needs and save $187,000 annually. A lifecycle analysis found positive net energy and avoided carbon emission benefits. Bioethanol from banana waste compares favorably to other feedstocks and could provide sustainable local fuel substitution without competing for food resources.

1. Environmental and economic assessment of bioethanol
production from Musa spp. waste
Sophie Graefe1, Luis Armando Muñoz1, Hortensia Solis2,
Roberto Mata2 & Alonso González1
1CIAT, International Center for Tropical Agriculture, Cali, Colombia, 2Coopedota, Costa Rica
Introduction
Musa spp. production systems generate large amounts of Household consumption
70
waste, as high numbers of fruits with no sufficient quality for Market
the market accumulate. 60 Animal feed
Waste
Due to its high starch concentration Musa waste has a high 50
potential to be processed into bioethanol, which can be used
40
as alternative fuel for farm machinery and vehicles.
%
The present study reports results of an environmental and 30
economic assessment of the potential to process bioethanol 20
from Musa waste within the region of a coffee cooperative in
10
the province of San José, Costa Rica.
The study area comprises 1500 ha small-scale coffee 0
plantations at altitudes between 1500 – 1900 m asl providing Guineo Plantain Banana
livelihood to ca. 780 families, where Musa spp. are commonly
grown to provide shade for coffee trees. Figure 1. Use of Musa spp. within the area of Coopedota, Costa Rica.
Materials and Methods Bioethanol processed from Musa waste could substitute 24% of
the gasoline demand of the cooperative, thereby saving
Semi-structured interviews were conducted with 80 farmers of
gasoline expenditures of 187,000 US-$ per year.
the cooperative to gather information on cultivation methods,
the availability and use of Musa biomass, as well as fuel The life cycle analysis resulted in a positive net energy balance
demands of households. Preliminary results of 38 interviews of 12.9 MJ L-1, with biomass transport representing the largest
are summarized below. energy demand along the production chain (Fig. 2).
An energy and carbon life cycle analysis was conducted in Avoided carbon emissions amount to 0.67 kg C L-1 when using
order to quantify energy inputs and C emissions along the Musa waste biofuel instead of conventional gasoline (Fig. 2).
whole biofuel production chain. This would yield in 129 t saved C emissions per year for the
whole area of Coopedota, assuming that the produced
bioethanol would be solely used by the cooperative members.
Results
97% of Coopedota farmers cultivate guineo, a nonplantain
cooking banana, followed by several banana varieties (68%)
4
and plantain varieties (63%).
Energy output / input ratio
More than 40% of guineo fruits are left to be rotten in the field, 3
and around one third are used as animal feedstock. Only a
small amount of guineo is used for home consumption or sold 2
on the market (Fig. 1).
More than 50% of plantain and banana are used for home 1
consumption; a considerable smaller percentage is sold on
markets or used as animal feed. The accumulation of waste 0
from plantain and banana is less than 15% of the total harvest Musa Sugarcane Corn Cassava
Costa Rica Brazil US Thailand
(Fig. 1).
Total fruit waste accumulation could amount to 2842 t yr-1 for
Figure 3. Energy output/input ratio of several bioethanol production systems.
the whole area of the cooperative. From this feedstock around
Data for sugarcane and corn were taken from De Oliveira et al. (2005) and for
192,866 L ethanol could be produced on a yearly basis (Fig. 2). cassava from Nguyen et al. (2007).
No farm inputs
Conclusions
Transport 22.0 kg ha-1 yr-1 Carbon
Carbon
emissions Avoided
The study showed a positive environmental as well as
emissions
23.1 kg ha-1 yr-1
conventional
gasoline
C emissions
0.67 kg L-1
economic impact for the processing of Musa waste into
0.85 kg L-1
Processing 1.13 kg ha-1 yr-1 bioethanol.
In terms of energy efficiency the system compares quite well
with other common biofuel feedstock (Fig. 3).
Availability of
Bioethanol yield
Musa waste does not compete for land resources or food, and
biomass could be therefore promoted as a sustainable small-scale
128.6 L ha-1 yr-1
1.89 t ha-1 yr-1
option for substituting fossil fuels for local consumption in
areas with large Musa waste accumulations.
No farm inputs
An effective operation requires the running of a processing
Energy Net-energy plant at a cooperative or village level.
Energy balance
Transport 1006 MJ ha-1 yr-1 concentration
requirements
1054 MJ ha-1 yr-1
bioethanol 1654 MJ ha-1 yr-1
or 12.9 MJ L-1
Further research is needed to quantify the amount of by-
2708 MJ ha-1 yr-1
Processing 48 MJ ha-1 yr-1 products generated through the processing of Musa waste,
and to assess its potential to recover nutrients that are
removed with harvest.
Figure 2. Key findings of the lifecycle analyses.
The financial support of FONTAGRO and CIM is gratefully acknowledged.