Devina Rankin
Executive Vice President & Chief Financial Officer at Waste Management
Thanks, John and good morning. The strong operating and financial results of the second quarter confirmed a number of important indicators we saw emerge in Q1, positioning us to increase our full year financial outlook. I'll cover our updated guidance in a moment but I want to give a little more color around our second quarter and year-to-date financials first.
As John discussed, our results have been driven by robust organic growth, led by our disciplined pricing focus as well as diligent cost management. Proactive management of our SG&A has been an important element of those cost management efforts. In the second quarter, adjusted SG&A was 9.4% of revenue, a 20 basis point improvement over the same period in 2021. We accomplished this result in spite of an increase in incentive compensation due to our focus on controlling discretionary SG&A spending and leveraging technology investments to reduce the customer sales and back office functions. We are on track to deliver SG&A as a percentage of revenue of about 9.6% for the full year.
Operating EBITDA increased more than $100 million in the second quarter, driven by an increase in the operating EBITDA of our collection and disposal business of $107 million. Operating EBITDA margin in the quarter was 28.1%, a 50 basis point improvement from the first quarter of 2022. We are confident in our ability to achieve our full year margin outlook which is a particularly strong result given the dilutive impacts from rising fuel costs which we now estimate could be about 60 basis points for the year.
Year-to-date cash flow from operations was up $142 million or about 6.5% from the prior year which has been driven by operating EBITDA growth of over 9%. Cash flow from operations growth was slightly muted relative to operating EBITDA growth due to higher cash taxes which will continue throughout the year and working capital pressure that we expect to moderate over the remainder of the year.
During the first half of the year, we've invested $856 million in capital to support the business and we invested an additional $112 million to support the strategic growth of our recycling and renewable energy businesses. Our year-to-date free cash flow which includes the impact of capital outlays to support our sustainability growth investments, is $1.35 billion, putting us on pace to exceed the upper end of our initial 2022 guidance of $2.05 billion to $2.15 billion.
While the pace of capital spending has been slower than expected in the first half of 2022, we currently expect truck deliveries, landfill construction and sustainability capital projects to ramp in the second half of the year. We're encouraged to see supply chain constraints in certain asset categories begin to show promising signs of improvement, though we are proactively managing the business in anticipation of the longer delivery schedules we've experienced over the last year. We will revisit capital and free cash flow guidance in more detail next quarter.
As Jim discussed, we are well positioned to allocate free cash flow among all our capital allocation priorities. In addition to increased acquisition expectations for the year, we now expect to allocate our full $1.5 billion authorization to share repurchases.
Turning now to our updated 2022 guidance. We expect revenue growth of approximately 10% and adjusted operating EBITDA in the range of $5.5 billion to $5.6 billion. The $175 million increase in operating EBITDA guidance is driven by more than $325 million from increased price and volume performance and $40 million from better performance in the renewable energy business. Those things are partially offset by approximately $190 million of higher costs which were driven by a combination of inflation pressure and incentive compensation.
Note that this outlook assumes fuel prices remain at June levels for the second half of the year, equating to a 60 basis point drag to full year operating EBITDA margin. Even still, we expect to deliver margin of 28.1% at the midpoint of our guidance. We remain optimistic that the alternative fuel tax credits will be approved in 2022 and continue to include the approximately $55 million benefit we would expect to receive in our outlook.
In closing, our excellent first half performance sets us up to deliver another year of strong financial growth in 2022. I can't thank the WM team enough for all their contributions to our success.
With that, Valerie, you let's open the line for questions.