Key barriers

Four key barriers in rice straw utilization are: logistics, fuel properties, business challenges and policy failures.

Logistics

Rice straw is a bulky and low-value material that is left in the field. The cost of handling and transporting it is high in terms of manpower, energy, and money.

Traditionally, rice has been harvested by had and carried, with the straw, to a threshing machine which separates them. In this system, ejected from the threshing machine, the straw ends in a heap. Today, increasingly, combine harvesters are taking over, driven by insufficient labor during harvest seasons. However, they need to be lighter than wheat combine harvesters, to avoid sinking in muddy paddy fields. Therefore, to keep the weight down, baling machinery is omitted and the combines simply scatter the rice straw. Hence, rather than helping to gather it, combine harvesters are making the logistics even more challenging and a separate baling machine is required. Since markets for the straw are not well developed, neither are the baling machines a mature technology.

Having gathered rice straw and taken it to the edge of the field, it still needs to be transported to a place of use. Rural rice producing areas of South and Southeast Asia often suffer from poor transport infrastructure that compounds the problem. There are also challenges in storage, especially when the straw is wet and the cost of drying would adversely affect the economics.

Fuel Properties

Below is a summary of the findings from the literature regarding rice straw composition.

Table 1. Composition analysis of rice straw.
HHT (MJ/Kg)	Proximate Analysis (%dry fuel)			Ultimate Analysis						Sources Analysis
HHT (MJ/Kg)	Fix C	Volatile	Ash	C	H	N	S	Cl	Ash	Sources Analysis
15.09	15.86	65.47	18.67	38.20	5.20	36.30	0.87	0.12	20.26	Jenkins, et al., 1998
	11.10	69.70	19.20							Braunbeck, 1998
14.57				35.94		1.18			22.00	Munder, 2013
14.079				33.70	4.00	1.71	0.16	0.32	29.10	Enertime, 2014

Table 2. Chemical composition of commonly used cereal straws (% DM) for livestock feeding
Compiled from Singh and Oosting (1993), Prasad et al., (1993), and Van Soest (2006).
Particular	Wheat straw	Rice straw	Barley straw	Oat straw
Lignin	8.5-15	6-10	11	14
NDF	75-82	65-80	80	70
ADF	51-64	49-59	59	47
SiO₂	1-5	13	2	2-5

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The high ash content, especially silica, makes combustion problematic due to fouling and slagging of boilers.

Non-technical (business challenges and policy failures)

Non-technical barriers include market failures, which comprise commodification, farmer cooperation, knowledge gaps, lack of proven business models, access to/cost of finance and fossil fuel subsidies ($1.9 trillion in 2011), and lack of effective policy support.