Rice Hulls as Alternative Building (RHAB): Productive Use of Agricultural Waste

EPA Grant Number: SU835294
Title: Rice Hulls as Alternative Building (RHAB): Productive Use of Agricultural Waste
Investigators: Williams, Michael
Institution: Butte College
EPA Project Officer: Page, Angela
Phase: II
Project Period: August 15, 2012 through August 14, 2014
Project Amount: $81,612
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2012) Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Agriculture , P3 Challenge Area - Built Environment , P3 Awards , Sustainability


The objective of this project is to provide an appropriate, environmentally acceptable disposal of agricultural waste, in this case, rice hulls which are left behind in huge quantities after harvesting and processing rice produced in Northern California and other rice producing areas in the United States and around the World. This is to be done by the development of structural insulating panels (SIPs) for use in residential and commercial building construction utilizing rice hulls as their primary raw material. Normally, structural insulating panels are made of a layer of Styrofoam panel sandwiched between two sheets of plywood. We plan to modify this concept to make use of rice hulls.


Our research in Phase 1 has showed promise. Thermal testing has confirmed our suppositions of the value of using rice hull as an insulator in structural insulated panels for building construction. Mechanical testing shows that our samples can compare to ordinary, already in use construction materials. There are more elements, however, that must go into the making of a panel for building purposes. As we move forward our research we are discovering additional issues associated with our potential product that we hope to examine from composition of appropriate ingredients in each panel to solving issues such as the occurrence of mold in one of our specimens. Challenges have repeatedly presented themselves to us, but with the focused investigations of the RHAB team as we move into P3 Phase II we are hopeful of resolving these issues.

Expected Results:

One issue that we ran into challenged our project as a whole. Cement is the binder that we feel offers the best results in our rice hull SIPs. Cement is very dense. As we began to make larger dimensional panels for testing, we found that the panels became feasible too heavy. We have been able to alleviate this problem by searching out other filler ingredients that allow for less cement input. One useful ingredient we found was styrofoam. We have been able to take used styrofoam and grind it down using a system we developed, incorporating the ground pieces as an ingredient in our panels. This is just one solution to our panel density issue.

Another solution that we crafted to reduce panel density is an adapt a method already being used in building construction. Rastra (made up of recycled Styrofoam and cement) is a method of building wall systems that follows very closely to how cinder blocks are used. The “blocks” are molded in such a way as to allow them on interlock when stacked vertically or butted together horizontally. There are cavities throughout the complete interlocking system that allows for reinforcement bar stabilization. After the re-bar is in place, cement is then poured into the wall. The cement cures and the wall system is complete. The “blocks” are often referred to as Insulated Concrete Forms ICF’s).

Supplemental Keywords:

rice hulls, rice hull insulated rastra block, SIP's, concrete insulated forms

Relevant Websites:

Phase 1 abstract

Progress and Final Reports:

  • 2013
  • Final

  • P3 Phase I:

    Rice Hulls as Alternative Building (RHAB) Project  | Final Report