The company's net debt was eliminated leaving net cash of £1.81 million (2009 net debt of £7.04 million). The company received a £9 million advance payment from Natural England for its Bolton Fell site.
Chief executive Bernard Burns said: "The doubling of our profits demonstrates the successful execution of our growth strategy. Our focus on customer service and product innovation and our extensive reserves of raw material have allowed us to win exciting new contracts and we are proud to supply premium brands to some of the most prestigious customers in the country.
"The recession has benefited William Sinclair with customers spending more time in their gardens as a more economical pastime than overseas holidays. We anticipate this trend will continue.
"The Group made a step change during 2010. Having built the necessary financial platform we were able to accelerate our growth strategy and, with our strong balance sheet and ambitious management team, we see further scope for expansion, both organically and by acquisition."
The figures, for the 12 months ended 30 September 2010, include the exceptional item of £0.46 million related to the impairment of its Oswaldtwistle site, currently held for re-sale.
Sales revenue in the year was £48.5 million which was a 4.7% increase on the previous year.
Sinclair said much of this increase was from growing media sales to retail customers "where we increased our share of a market which held up well in recessionary conditions. Strong sales growth at Freeland was helped by sales of top soils to Olympic sites which more than compensated for sales reductions to a badly recession-affected construction industry."
In June 2010 Freeland launched a synthetic peat substitute (SuperFyba), which uses garden waste that previously went to landfill.
In April 2010 Sinclair received a £9 million advance payment from Natural England as part of an agreement to cease peat harvesting at Bolton Fell in Cumbria.
Sinclair's full claim was submitted in October 2010 and is for a "substantially higher figure", to be fully resolved before the end of November 2013 when activities on site must be complete.
Peat-free New Horizon compost sales grew during the year by 39% compared with growth of 23% for the peat-free market in general.
The group announced in November 2010 the acquisition of the assets and trade of Growing Success Organics from Monro and, in early December, an aggregate business. The total cost of the two acquisitions was £1.1 million. The acquired businesses should contribute approximately £5 million of turnover in a full year.