This hearty and healthy burger uses ingredients that would normally be tossed into the trash to help cut down on food waste. The patty is made from the pulp that comes after making fresh vegetable juices.
Preheat the oven to 375°F.2.
Spread the beet pulp evenly on a parchment paper–lined rimmed baking sheet. Spread the carrot pulp evenly on a second parchment-lined baking sheet. Roast for about 30 minutes, stirring occasionally, until the pulp is dry and browned in spots. Scrape into a bowl and let cool completely. Leave the oven on.3.
In a bowl, toss the mushrooms with the kidney beans, tofu and canola oil together. Spread the mixture, in an even layer, onto a baking sheet and roast for 30 minutes, stirring occasionally, until browned and dry.4.
In a food processor, pulse the spelt until finely chopped; scrape into a large bowl. Add the mushroom mixture to the processor and pulse until finely chopped; add to the bowl. Add the roasted beet and carrot pulp, the celery pulp and all of the remaining burger ingredients and mix well. Pack the mixture into four 1/2-inch-thick burgers.5.
Heat a grill pan over a medium-high flame. Spread the butter on the buns and toast cut side down over moderate heat until golden, about 2 minutes. Transfer the buns to a plate.6.
Brush the grill pan with oil. Add the burgers and cook over moderate heat, turning once, until nicely charred, approximately 3 minutes per side.