Spent oil re-refining firm HydroDec slid further into the red in the first half of 2011 despite a 26% increase in revenue, but sales volumes and gross unit margins both increased over the same period last year. Loss-before tax was $5.36m, versus a loss of $4.28m in the same period the previous year, while revenues grew from $8m to $10.1m, driven by higher pricing and more favourable market conditions.Sales volumes increased to 9.5m litres from 9.4m in the corresponding period of 2010. Volume growth was lower than expected as the group held the line on pricing in the acquisition of feedstock from the spot market while building long term relationships with quality suppliers. Gross unit margins improved significantly to $0.21 per litre from $0.18 per litre last year, as the group's strategy to diversify its customer base and address new applications resulted in higher selling prices.Loss per share deteriorated slightly from -1.50 cents to -1.47 cents.Chairman Neil Gaskell said: "Hydrodec's existing operations are progressing well, margins are improving and the development of the joint venture in Japan remains on track. As our feedstock availability steadily improves, Hydrodec is moving into higher gear with the development of a new strategic plan, including a further strengthening of the leadership team, to support expansion." Demand for the group's cleantech industrial oils was robust with revenues and volumes continuing to improve in the first half. Feedstock availability is improving gradually as the group forges relationships with major providers such as utilities to provide a consistent and stable supply for the long term.The company's gross unit margins increased 17% to $0.21 per litre (H1 2010: US$0.18 per litre) and it secured £2m in debt financing. Cash grew from $0.3m to $1.2m at the end of June. NR