Revenue and adjusted EBITDA in Q2 increased 17.5% and 23%, respectively, over the prior year period, primarily as a result of continued improvement in solid waste pricing volume growth and strength in recovered commodity values.
These trends drove year-to-date adjusted EBITDA margin expansion of 110 basis points and adjusted free cash flow of over $585 million, up 18.5% year-over-year, and given expected continuing momentum and margin expansion from these trends position us to raise our full year outlook for revenue, adjusted EBITDA, adjusted EBITDA margin and adjusted free cash flow.
Year-to-date, we have signed or closed 14 acquisitions with total annualized revenue of approximately $115 million, including $75 million of franchise operations in California, Nevada and Oregon expected to close later this year.
In the second quarter, solid waste price plus volume growth of 11.4% exceeded our expectations by almost 150 basis points, primarily as a result of higher-than-expected volumes as the recovery trends that began in Q1 continued throughout the quarter, with landfill tons and roll-off pulls returning to levels about in line with or above prepandemic levels.
Total price of 4.9%, up 70 basis points sequentially, was above our outlook on higher core pricing of 4.7%, once again reflecting the strength of pricing retention we noted in Q1, plus about 20 basis points in fuel and material surcharges.
Our Q2 pricing ranged from 2.6% in our mostly exclusive Western region to a range of about 4.5% to 7% in our more competitive regions.
Reported volume growth of 6.5% in Q2 reflected sequential improvement of approximately 1,000 basis points from Q1 and was led by those regions where markets were hardest hit during the pandemic including the Northeast U.S. and Canada.
Volumes range from about 4% in our Central region, where comparisons to the prior year were tougher as many markets were relatively less impacted by the COVID-19 pandemic, to almost 10.5% in Canada, one of our most impacted regions where the volume recovery have been remarkably strong, arguably outpacing the reopening activity particularly when considering that many restrictions in Canada extended through Q2 of this year.
Also noteworthy is our Western region, where volumes led our other regions going into the pandemic and continue to be the strongest in the U.S. at about 8.5% in Q2.
Looking at year-over-year results in the second quarter on a same-store basis, all lines of business increased by double digits Commercial collection revenue was up 16% year-over-year.
Roll-off pulls increased by over 11% year-over-year, led by Canada, up almost 20% and back to above pre-COVID-19 levels.
In the U.S., pulls were up about 10%, and all regions showed year-over-year improvement, most notably in our more impacted markets, including in the Northeast.
Landfill tons were up 17% year-over-year on MSW tons up 11%, C&D tons up 20% and special waste tons up 33%.
However, the outsized amount of special waste activity was particularly noteworthy as Q2 activity propelled tons back to 13% above pre-pandemic levels with all regions up year-over-year, perhaps due to a little pull forward from Q3.
Excluding acquisitions, collectively, they were up about 95% year-over-year resulting in a combined margin tailwind of about 130 basis points, 90 basis points of which was from recycling and 40 basis points from landfill gas and RINs.
Recycling revenue increases were driven by both higher commodity values, including old corrugated containers or OCC, up 25%; and plastics and metals, both up over 100%.
Prices for OCC averaged about $135 per ton in Q2 and our RIN pricing averaged about $2.72.
We reported $31.2 million of E&P waste revenue in the second quarter, up 26% sequentially from Q1, reflecting increased activity across multiple basins.
As noted earlier, we've already signed or closed 14 acquisitions with annualized revenue of approximately $115 million, approaching what we would consider an average amount of activity for the full year.
In the second quarter, revenue was $1.534 billion, about $44 million above our outlook due primarily to higher-than-expected solid waste growth and recovered commodity values.
Revenue on a reported basis was up $228 million or 17.5% year-over-year, including acquisitions completed since the year ago period which contributed about $47.6 million of revenue in the quarter or about $44.1 million net of divestitures.
Commodity-driven impacts account for about 100 basis points of margin expansion, net of a 30 basis point impact from higher fuel on diesel rates up almost 20% year-over-year.
Ex fuel solid waste collection transfer and disposal margins expanded by 50 basis points as we more than offset a 60 basis points increase in incentive compensation costs, 50 basis points from higher medical and 50 basis points from increased discretionary expenses.
And finally, acquisitions completed since the year ago period accounted for about 10 basis points of margin dilution.
As noted earlier, we've already implemented incremental price increases to address these higher costs, resulting in full year 2021 price of approximately 5%, up from 4% in our original outlook.
We delivered adjusted free cash flow up 18.5% year-over-year through Q2 at $585 million or 20% of revenue, putting us on track to achieve our revised adjusted free cash flow outlook of approximately $1 billion.
Revenue in Q3 is estimated to be approximately $1.56 billion.
We expect solid waste price plus volume growth of about 7% in Q3 with pricing of about 5%.
Adjusted EBITDA in Q3 is estimated to be approximately $495 million or 31.7% of revenue, up 60 basis points year-over-year and up sequentially from Q2.
Depreciation and amortization expense for the third quarter is estimated to be about 13.3% of revenue, including amortization of intangibles of about $33.8 million or a rounded $0.10 per diluted share net of taxes.
Interest expense, net of interest income, is estimated at approximately $40 million.
And finally, our effective tax rate in Q3 is estimated to be about 21.5%, subject to some variability.
Revenue for 2021 is now estimated to be approximately $5.975 billion or $175 million above our initial outlook, with the primary drivers being an additional 150 basis points of solid waste price plus volume growth and higher recovered commodity values as compared to our initial outlook, plus $25 million from acquisitions completed year-to-date.
Adjusted EBITDA for the full year is now estimated to be approximately $1.875 billion or about 31.4% of revenue and up about $75 million over our initial outlook.
Moreover, full year adjusted EBITDA margin guidance is 40 basis points above our initial outlook, up 90 basis points year-over-year.
At 31.4%, our adjusted EBITDA margin outlook reflects continued year-over-year margin expansion in the second half of 2021 in spite of wage and inflationary pressures and tougher year-over-year comparisons.
Adjusted free cash flow in 2021 is now expected to be approximately $1 billion or over 53% of EBITDA and up $15 million from our initial outlook despite capex up $50 million from our original outlook.
Last week, we closed our new $2.5 billion credit facility, which increased borrowing capacity by almost $300 million, reduced borrowing spreads and enhanced flexibility for continued growth.
We have already returned over $400 million to shareholders in 2021 through share repurchases and dividends.
And we are in the process of renewing our normal course issuer bid, authorizing the repurchase of up to 5% of our outstanding shares per annum.
We are on track for adjusted free cash flow of approximately $1 billion and adjusted EBITDA margins back above pre-COVID-19 levels.

Summary:
Revenue on a reported basis was up $228 million or 17.5% year-over-year, including acquisitions completed since the year ago period which contributed about $47.6 million of revenue in the quarter or about $44.1 million net of divestitures.
Revenue in Q3 is estimated to be approximately $1.56 billion.
We expect solid waste price plus volume growth of about 7% in Q3 with pricing of about 5%.
Revenue for 2021 is now estimated to be approximately $5.975 billion or $175 million above our initial outlook, with the primary drivers being an additional 150 basis points of solid waste price plus volume growth and higher recovered commodity values as compared to our initial outlook, plus $25 million from acquisitions completed year-to-date.