In this chapter, we show that while the carbon emission allowance futures market, which is still emerging, has gained relative little popularity among investors it can present attractive diversification opportunities for investors. Our findings show that the exposure of these futures returns to equity returns as well as the value factor is low but increases with stock market stress. As our further analysis suggests that investors can also profit from negative convenience yield in carbon emission futures by taking short positions in them, the strategy can be an attractive addition to equity portfolios. We note that potential reasons for the lack of popularity are poor liquidity, lack of investors' attention to the investments, investment ambiguity, and investment constraints. Nevertheless, carbon emission allowances and environmental investments of its kind can be important portfolio diversifiers in future.