Munroe stopped Victor Terrazas in the ninth round of Friday's eliminator and will face Japan's Toshiaki Nishioka.
's Montour plant near Washingtonville, Pennsylvania, generate 500, 000 tons of gypsum annually, plant manager Michael Munroe said.
And Munroe says his work ethic and attitude means he has nothing to fear from his next fight.
Nishioka, 34, rocked Munroe in the fifth, seventh and 10th as he proved too classy for the British fighter.
BBC: Rendall Munroe loses super-bantamweight world title bid
Two big shots from the Spaniard in the first round suggested he would be up against it but Munroe regrouped superbly.
Nishioka quickly settled into his rhythm with trademark snappy combinations but Munroe's defence was solid and he too made a confident start.
BBC: Rendall Munroe loses super-bantamweight world title bid
Munroe, 28, had won his crown by a majority decision over Martinez and had clearly learned much in his three subsequent fights.
Munroe, 30, suffered only his second defeat, losing a unanimous decision with all three of the judges in Japan scoring the fight 119-109.
BBC: Rendall Munroe loses super-bantamweight world title bid
Promoter Frank Maloney is the man who will set up the shot at the world title but Munroe will first think about taking a well-earned break.
He started strongly and inflicted a cut over his opponent's left eye but Munroe gradually took control and was well ahead on all three judges' scorecards.
But Munroe came back into the fight in the fourth as he upped his work rate, catching his opponent with an accurate left hook midway through the round.
BBC: Rendall Munroe loses super-bantamweight world title bid
Also on the lookout is Tommy Munroe, 21, a music student and singer-songwriter from Woking, Surrey, who stuck up a friendship with anarchists while performing on London's alternative scene.
It was a body shot which again rocked Munroe in the seventh but a cut above the right eye of Nishioka gave the challenger hope just before the bell.
BBC: Rendall Munroe loses super-bantamweight world title bid
"That side of things doesn't concern me, " Munroe reflected.
Munroe was troubled in the sixth with Nishioka's right jab, left hook combination finding the target far too often, while the champion also started to work the body of the Leicester fighter.
BBC: Rendall Munroe loses super-bantamweight world title bid
Munroe's defence was weak by the latter stages of the fight as Nishioka's jab continued to break his guard but despite some more desperate moments for the Briton, he held on until the final bell.
BBC: Rendall Munroe loses super-bantamweight world title bid
Enter web-comic celebrity Randall Munroe (of xkcd), and his friend Ellen, Senior Reactor Operator at the Reed Research Reactor, who have put together some charts which might help us make sense of all this radiation talk.
The champion was the busier fighter in the second and third as he landed the cleaner punches, with his jab proving a dangerous weapon, while also proving an evasive target as Munroe was made to miss far too often.
BBC: Rendall Munroe loses super-bantamweight world title bid
The ninth was a good round for Munroe as Nishioka looked as if he was beginning to tire, but the Japanese fighter proved as effective off the back foot, hurting his opponent with another body shot in the 10th, as he looked to close out the fight.
BBC: Rendall Munroe loses super-bantamweight world title bid
By the time the eighth came around Munroe was well behind on points and although he tried to assert himself on the fight Nishioka's movement was too cute, as he continued to break the spirit of the Leicester man with accurate body shots, while also opening up a cut below his right eye.
BBC: Rendall Munroe loses super-bantamweight world title bid
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