Assessing the potentials of agricultural residues for energy: What the CDM experience of India tells us about their availability
Introduction
Agricultural residues are generated proportionally to annual crops, in billions of tonnes each year in the world. They are generally called primary or secondary whether originating from crop harvest or transformation processes respectively. Mainly being co- or by-generated along with food products, crop residues promise cheaper biomass to the energy sector than dedicated plantations, as well as complementarities instead of competition between food and energy.
The potential of crop residues for energy has been assessed in various global and national outlook studies, on the basis of aggregate agricultural data from sources such as FAOSTAT and using simple ratios (Guille, 2007, Milhau, 2012a). Technical constraints on residue harvesting and logistics are considered (Vis, 2010), as well as priority uses for soils and local livestock (Lal, 2005, Williams et al., 1997).
Assessments of potentials take into account that all the residues are not available and commonly agree on the necessity to better understand the different and often interdependent soil and livestock needs (Richard and Guérin, 2010). Resulting volumes of potentially available residues generally represent a non-negligible potential source of energy on which the development of second generation biofuels could rely (Smeets et al., 2007, Haberl et al., 2007, Scarlat et al., 2010). However, until recently little attention has been given to the existing energy uses of agricultural residues. They either represent traditionally low-efficiency uses, along with fuel wood combustion in poor rural areas (Sagar, 2005), or may appear too punctual and site-specific, to be representative of new renewable energy developments.
In that context, India stands out with hundreds of projects designed in response to the opportunities offered by the clean development mechanism (CDM) since 2004. The conditions in which industrial energy uses of agricultural residues have recently boomed in India, give indications about the practical availability of this biomass for large industrial uses and how it compares with initially assessed potentials.
In an attempt to systematically draw lessons from India's unique experience and to better understand the meaning and implications of biomass potential assessments, we first review potential assessments of agriculture residues for energy in India and conduct our own updated assessment. We then analyze the Indian context for CDM bioenergy projects and all the publicly available documentation on successfully registered projects. This allows us to identify the specific set of conditions allowing for the energy use of agricultural residues, study how far these conditions can be sustained and determine the possible threshold effects. Our results are the basis of contrasted storylines for scenarios on biomass availability and price.
Section snippets
Assessing the potential of agricultural residues for industrial energy uses
Crop residues potential availability for energy production can be defined as the production surplus that is not utilized for immediate purposes. Basically, it is the difference between crop residue production on the supply side and residue agricultural consumption on the demand side.
The availability of crop residues for energy purposes has been assessed at global, regional and local scales (Berndes et al., 2003, Guille, 2007, Milhau, 2012a). Generally potentials are assessed in a rather
India currently gains experience on the exploitation of crop residue potentials
In 2010 the Ministry of New and Renewable Energy (MNRE) of India mentioned a total of 288 projects producing a total of 2665 MW with crop residues (MNRE, 2011). A total of 158 projects use sugarcane bagasse, whereas the others use various types of residues. From 2004 and until August 1st 2010, 136 projects out of the 288 censed by the government, were successfully registered by the CDM Executive Board. Those projects were screened on the basis of all the publicly available documentation: CDM
The possible thresholds in the further exploitation of biomass potentials for energy
Looking at 7 CDM projects with enough detailed financial information, we can investigate the negative impact of a ten percent fuel cost increase on the internal rate of return (IRR), and calculate what would be necessary to get back to the expected IRR. In our assumptions, these options are only used independently:
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Tariff increase, a higher price for the electricity sold to the grid.
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Reduction of project costs, that sums the investments of the project. In all but one project, operation and
Discussion: scenarios on biomass availability and prices
The socio-economic and environmental impacts of residue mobilization for energy are contemplated within 3 different scenarios that could be built with further investigation on site. In a first attempt to distinguish possible futures, we briefly describe three storylines below, characterize them in Table 9 and offer to visualize them in Fig. 8 through the contrasted trajectories of the main parameters and variables of residues-to-energy projects.
Conclusions
In many countries with significant agricultural production, crop residues might represent important potentials for industrial production with regards to their current low levels of use and the relative inefficiency of traditional energy uses. However, the experience of India tells us to beware of exhaustion effects that might rapidly appear and negatively affect the viability of biomass-to-energy projects. In India, some residues, mainly secondary ones such as sugarcane bagasse and rice husk,
Acknowledgments
The authors wish to thank the chair New Strategies for Energy (NSE) and the CIRAD (International Cooperation Centre on Agricultural Research for Development) for their financial support and interest. This work benefitted from the preliminary findings of Thomas Guille, as well as from the ideas and comments of Dominique Dron and Philippe Girard. Thank you to the anonymous reviewer and to Janice Vargas who helped improve the article.
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