Growing public concern regarding the environment and strive towards use of renewable resources represent key drivers for governments, companies, and researchers to develop alternatives to petroleum-based plastics. Replacing petro based plastics by bio based needs a transition period during which both petro and bio based plastics will coexist on the market. At the same time demand for products made from recycled materials is rising, making recyclability an important attribute for many types of plastics. Polymer blends and alloys offer an interesting solution to obtain multipurpose materials with tailor-made properties. However, recycling of these inseparable mixtures is restricted by processing as well as thermodynamic issues. As a part of the project “Sustainable recycling of “green” plastics” a study on the recycling and other challenges related to blends of bio- and petro based plastics has been done. PLA blends with HDPE and with PC has been investigated along with PVC plasticized with a bio-based plasticizer. The work has been performed by simulation of pre- and postconsumer products recycling. High throughput laboratory methods and industrial scale processing were used. Effects of recycling were investigated using sensitive analytical tools as well as tests of mechanical strength.