MELBOURNE (Reuters) - A new renewable energy source has emerged in Australia with the development of the world's first power station to be fueled by waste macadamia-nut shells. Construction began this week on the A$3 million ($2 million) power plant in the northern state of Queensland, which will use 5,000 tonnes of shells annually from Australia's native macadamia nuts as fuel for the 1.5 megawatt generator. The biomass co-generation plant, which is a joint venture between Queensland state-owned Ergon Energy and macadamia nut producer Suncoast Gold Macadamias, will generate 9.5 gigawatt hours of electricity annually to supply more than 1,200...