Use a refillable stainless steel capsule with your own ground coffee, or switch to a cafetiere, stovetop or filter. If you keep capsules, use the brand's take-back scheme.
A plastic capsule is around 3 g; one a day is about 1.1 kg a year. Compostable capsules are usually PLA and need industrial composting; University College London (UCL)'s Big Compost Experiment found most home-compostable-labelled items did not disappear in real heaps.
The catch: refillable pods take a minute to fill and tamp, and results vary by machine; aluminium capsules are recyclable only through dedicated take-back.