Valorization of Waste Feathers in the Production of New Thermal Insulation Materials

Abstract

Poultry has become the primary source of dietary protein consumed globally and as a result the by-product feathers are an increasingly problematic industrial waste. Developing a circular economy for feathers is, therefore, an important research area that provides an opportunity to make use of the unique combination of properties of this abundant natural material. This paper reports on the thermal properties of novel feather-based thermal insulation materials. Waste feathers were collected, cleaned and processed into fibres, which were then used to form air-laid nonwoven materials. These have a high fibre content and exploit the excellent natural thermal insulation properties of feathers. The performance of the novel materials developed are tested in order to outline the influence of temperature and density on thermal conductivity and dynamic water sorption. Results are compared to a range of commercially available thermal insulation materials for buildings manufactured from denim, hemp, sheep wool, PET and mineral wool. It was found that air laid feather-fibre fabrics have comparable performance to other fibrous materials and have a thermal conductivity of 0.033 W/(m K) for samples with a density of 59 kg/m 3. This is due to the low thermal conductivity of feather fibres and the void structure formed by air-laid processing that effectively traps air. These materials additionally offer improved sustainability credentials as they are derived from a readily available waste that is generally considered to be unavoidable. The paper concludes by highlighting the significant technical and commercial barriers that exist to using waste feathers in thermal insulation products and suggests areas for further research that can exploit the unique properties of feathers.

Heat Transfer in Straw-Based Thermal Insulating Materials

“…Both straw types show a similar trend in terms of changing bulk density, and we measured the lowest thermal conductivity for both Type-1 and Type-2 straw bulks at 120 kg/m 3 bulk density, which can be considered the optimum bulk density. This optimum bulk density is higher than that of mineral wool or bagasse (100 kg/m 3 ), hemp or palm fiber (90 kg/m 3 ), flax fiber (80 kg/m 3 ), feather fiber (60 kg/m 3 ) or wood wool (50 kg/m 3 ), respectively [ 20 , 50 , 64 , 65 ].…”

“…Specimens were prepared according to EN 12667 and EN 1946-2 [ 57 ], respectively. The investigated bulk density range of the straw samples was between 80 and 180 kg/m 3 in the case of both types, not only to calibrate or validate our model, but also to identify the optimal bulk density that gives the lowest possible thermal conductivity and can often be found for natural fibrous thermal insulations [ 20 ].…”

“…Such materials are, among several other used natural alternatives such as bark, cellulose, hemp, kenaf, flax, feathers, sheep wool, or wood fibers [ 7 , 19 , 20 , 21 ], the natural vegetable fiber-based thermal insulations that are gaining ground in the construction market [ 22 ] because demand for green building materials is rising sharply [ 23 ]. Among natural fibers, one of the most researched materials is the use of straw bales as building materials [ 24 , 25 ] because of their low thermal conductivity and high specific heat capacity, and hence low thermal diffusivity and good thermal insulation capability, especially with fibers randomly oriented and perpendicular to heat flow, and low environmental impact if the straw bale selection used for the straw-based building is suitable [ 26 ].…”

“…However, the models were created for mineral wools and aerogel blankets, but the equations prescribed for these materials had to be changed or supplemented to be able to describe the presented straw material properly. For example, a straw model needs a more accurate material property description because of the nature of the stems and because some of the natural state or loose-filled thermal natural thermal insulations are especially sensitive to bulk density changes [ 20 , 48 , 49 , 50 ]. In the case of the first base model [ 45 ], the material density and the bulk density of the insulation were sufficient because the glass fibers are both solids.…”

Effect of drying method on compressive strength of straw-based thermal insulations

“…The most common natural raw materials for thermal insulation are flax, hemp, sheep wool, corn husk, cotton, coconut husk [8][9][10][11]. Some sustainable insulation reaches the thermal insulation performance [12], durability, usability, or mechanical properties of artificial insulations, but these properties usually not combined in one product [13]. This fact hinders the spread of these environmentally conscious materials.…”