Novel insulating construction blocks of crop residue (straw) and natural binders

Abstract: This research aimed to develop an insulating construction block with low embodied energy and high carbon sequestration formed from post grain harvest wheat straw, an agricultural crop residue, using a natural clay binder. The mechanical properties of Lightweight Straw and Clay Blocks (LSCBs) with various orientations of straw and concentrations of clay binder were measured and compared. Thermal conductivity of a 20 cm LSCB cube with a compressive strength of 112 kPa was lower when the direction of heat flow was perpendicular to (across) the wheat straw stalk orientation (0.066 W/mK) than parallel to the length of the stalk (0.094 W/mK). LSCBs can be used as self-supporting and carbon-sequestering insulation building blocks in lieu of concrete masonry units (CMU). Graphical abstract: (Figure presented.) Highlights: Lightweight Straw and Clay Blocks (LSCBs) developed in this research project for building insulation are fabricated from post-harvest crop residue. They are self-supporting, carbon-sequestering insulation material that when used in construction can reduce the embodied energy of the building and decrease the building’s energy consumption. Discussion: Can traditional straw and earth composites be reformed as insulation necessary to reach current energy consumption and GHG emission reduction goals? Straw bales are sustainable insulation due to low conductivity, high carbon sequestration, and are an unprocessed agricultural waste product. The problem is straw-bale building demands significant modifications in modern construction techniques and elements. Currently marketed plant-based insulation materials are not self-supporting, therefore require engineered supporting elements Many plant-based engineered products have high embodied energy fabrication processes such as chemical binders, high heat, and high pressure which result in high density which increases their thermal conductivity This research exploits common clay as a lightweight binder to form conventional style, insulating construction blocks. Together with the perpendicular alignment of all of the stalks to the flow of heat, low conductivity is maintained and increases the block’s compressive strength The vertical alignment of the stalks significantly increases the block’s compressive strength.