Assessing the potentials of agricultural residues for energy: What the CDM experience of India tells us about their availability

Highlights

• India generates 572.10⁶ t crop residues, 15–25% are potentially available.

• Registered CDM projects for electricity generation use 17% of this energy source.

• Some residues will be exhausted before the implementation of planned projects.

• Residue scarcity translates to new markets with rising prices.

• Increased tariffs will be necessary to compensate biomass cost increase.

Abstract

The potential of agricultural residues has been assessed worldwide and at different scales. Interpreting results so as to determine the possible role of this biomass feedstock in energy supplies, requires a clearer understanding of the conditions in which residues can effectively be mobilized for energy production. The experience of India with hundreds of projects where agricultural residues are transformed to heat and power partially sold to the grid, is analyzed and checked against the residue potentials that have been assessed in this country. We find that, in the absence of technological improvements in biomass conversion, the apparent success of Indian bioenergy projects is not sustainable in the long run due to rapid exhaustion effects on residue availability, coupled with the increasing costs that would be difficult to compensate by higher electricity tariffs. We also identify there is a serious agricultural issue which needs to be addressed in regard to degraded soils; this could lead to the reallocation of all primary residues, as well as part of secondary residues to soil and livestock needs. Such perspectives are considered within three contrasted scenario storylines.

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.