*Article* **Sustainability Evaluation of Polyhydroxyalkanoate Production from Slaughterhouse Residues Utilising Emergy Accounting**

**Khurram Shahzad \*, Mohammad Rehan , Muhammad Imtiaz Rashid , Nadeem Ali, Ahmed Saleh Summan and Iqbal Muhammad Ibrahim Ismail**

> Centre of Excellence in Environmental Studies, King Abdulaziz University, Jeddah 21589, Saudi Arabia; dr.mohammad\_rehan@yahoo.co.uk (M.R.); irmaliks@gmail.com (M.I.R.); nbahadar@kau.edu.sa (N.A.); asumman@kau.edu.sa (A.S.S.); iqbal30@hotmail.com (I.M.I.I.)

**\*** Correspondence: ksramzan@kau.edu.sa or shahzadkhu@gmail.com

**Abstract:** High raw material prices and rivalry from the food industry have hampered the adoption of renewable resource-based goods. It has necessitated the investigation of cost-cutting strategies such as locating low-cost raw material supplies and adopting cleaner manufacturing processes. Exploiting waste streams as substitute resources for the operations is one low-cost option. The present study evaluates the environmental burden of biopolymer (polyhydroxyalkanoate) production from slaughtering residues. The sustainability of the PHA production process will be assessed utilising the Emergy Accounting methodology. The effect of changing energy resources from business as usual (i.e., electricity mix from the grid and heat provision utilising natural gas) to different renewable energy resources is also evaluated. The emergy intensity for PHA production (seJ/g) shows a minor improvement ranging from 1.5% to 2% by changing only the electricity provision resources. This impact reaches up to 17% when electricity and heat provision resources are replaced with biomass resources. Similarly, the emergy intensity for PHA production using electricity EU27 mix, coal, hydropower, wind power, and biomass is about 5% to 7% lower than the emergy intensity of polyethylene high density (PE-HD). In comparison, its value is up to 21% lower for electricity and heat provision from biomass.

**Keywords:** biopolymers; sustainability; emergy accounting; polyhydoxyalkanoates; slaughterhouse residues
