Apprenticed to wire working at 13 years of age, Greening soon became involved in reform movements. His first public speech came three years later when he addressed the Anti-Slavery Society Manchester. He was active in the Union and Emancipation Society and the suffrage movement. He stood for parliament at Halifax in the election of 1868 as a working class candidate.
His involvement with the co-operative movement dates from the mid 1850s onwards. He knew many of the Owenites (followers of Robert Owen) including William Pare, Lloyd Jones, ET Craig and GJ Holyoake. Greening was involved in the events leading to the convening of the first modern Co-operative Congress in 1869 and the formation of the Co-operative Union. He played a prominent part in the formation of the International Co-operative Alliance. His other interests included productive co-operative societies and agricultural and horticultural co-operatives. He was editor of The Agricultural Economist and the One and All Gardening Annual. He also encouraged co-operative societies to support sport, art and hobbies – he initiated the Crystal Palace Festival and organised co-operative concert parties.